Pathological Remodeling Research Articles

Abstract Tu075: Cardiac macrophages expressing CD206 and IL-4Ra are required for adverse LV remodeling in HF

Cardiac macrophages significantly expand in chronic heart failure (HF). We tested the hypothesis that CD206 + macrophages expressing interleukin (IL)-4Ra in the failing heart are key drivers of left ventricular (LV) remodeling and ischemic cardiomyopathy. Cardiac macrophages were profiled using flow cytometry in adult male C57BL/6 (WT) mice following non-reperfused myocardial infarction (MI) to induce HF or sham operation. CD206 + macrophages progressively expanded in post-MI hearts during the progression of LV remodeling and comprised ~85% of macrophages at 8 w. These macrophages were exclusively proliferative and predominantly C-C motif chemokine receptor (CCR2) – and major histocompatibility complex (MHC)II hi in failing hearts, with the majority (92%) of CD206 + CCR2 – macrophages expressing LYVE-1, an embryonically-derived resident macrophage marker. Nearly half of cardiac CD206 + macrophages expressed IL-4Ra; the abundance of CD206 + IL-4Ra + directly correlated with LV dysfunction and fibrosis. Intramyocardial adoptive transfer of IL-4-polarized bone marrow derived CD206 + macrophages induced progressive LV dilation, dysfunction and fibrosis over 4 w in naïve recipient mice. To evaluate the role of CD206 + IL-4Ra + macrophages in LV remodeling, we used male and female LysM CreERT2 ;IL-4Ra F/F mice that allow for inducible myeloid-specific IL-4Ra gene deletion. Administration of tamoxifen from at 4 to 10 w post-MI (in established HF), effectively deleted IL-4Ra in cardiac macrophages and significantly reduced CD206 + macrophage abundance and proliferation in the remodeling heart. Myeloid-specific IL-4Ra deletion further prevented LV remodeling progression, improved fibrosis and neovascularization, and alleviated LV systolic dysfunction, while suppressing expansion of cardiac immune cells and blood Ly6C high monocytosis. We conclude that an expanded and proliferative population of CD206 + IL-4Ra + macrophages primarily derived from resident macrophages are key mediators of pathological LV remodeling and fibrosis. Inhibition of CD206 + macrophage IL-4Ra signaling may be a fruitful therapeutic approach to alleviate disease progression in HF.

Abstract Tu089: p21 Regulates Hypertrophic Cardiomyopathy Remodeling By Inhibition of Cardiomyocyte Endoreplication

Background: We previously discovered that a murine model of hypertrophic cardiomyopathy had increased cardiomyocyte endoreplication and replication stress leading to increased DNA damage. Activation of DNA damage response pathways was associated with increased cardiomyocyte expression of the cyclin-dependent kinase inhibitor p21. However, the role of p21 on pathologic myocardial remodeling in hypertrophic cardiomyopathy is poorly understood. Methods: We utilized a murine model of hypertrophic cardiomyopathy that is deficient in cardiac myosin binding protein 3 (Mybpc3 -/- ). We used murine models deficient in p21 (Cdkn1a -/- ) or overexpressed p21 (Cdkn1a SUPER ) to determine the role of p21 on hypertrophic remodeling. Heart structure and function were evaluated by echocardiography. Flow cytometry and immunohistochemistry were used to measure cardiomyocyte DNA content and ploidy. Proteomics and biochemical assays were utilized to identify p21 target proteins. Results: We observed that there was an increased p21 expression in Mybpc3 -/- cardiomyocytes during the postnatal day 7 to 25 time interval. Elimination of p21 expression in Mybpc3 -/- animals (Cdkn1a -/- /Mybpc3 -/- ) caused increased myocardial hypertrophy (Table 1). Conversely, selective overexpression of p21 in cardiomyocytes (Cdkn1a SUPER /Mybpc3 -/- /Myh6Cre) led to reduced myocardial hypertrophy (Table 1). We discovered that isolated cardiomyocyte nuclei from Mybpc3 -/- mice with reduced p21 had increased polyploidy whereas overexpression of cardiomyocyte p21 led to reduced cardiomyocyte polyploidy (Table 1). Using both proteomics and targeted assays we discovered that cardiomyocyte p21 was binding to key cycle regulatory proteins to inhibit cardiomyocyte endoreplication and hypertrophic growth. Conclusions: Collectively, our results show that induction of p21 in hypertrophic cardiomyopathy reduces cardiomyocyte growth by inhibiting endoreplication.

Abstract Or109: Regulation of UFM1 modification from ER dynamics to cardiac homeostasis

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity globally. Understanding the molecular mechanism governing CVD has become a major focus in developing new therapeutics. Ubiquitin (Ub) like protein post-translational modifications (PTMs) have been known to play an important role in the normal functioning of the heart. UFM1 (ubiquitin-fold modifier 1) is a novel Ub-like protein that covalently modifies protein substrates via a highly conserved E1 (UBA5)-E2 (UFC1)-E3 (UFL1) enzymatic cascade, named ufmylation. Ufmylation regulates diverse cellular processes and is implicated in various human diseases. However, its importance in the heart is unknown. For the very first time, we have reported dysregulation of ufmylation in dilated cardiomyopathy, hypertrophic human patients, and animal models. It remains unclear whether ufmylation of cardiac proteins is required for heart function and if so, how ufmylation regulates cardiac function. To determine the role of UFM1 modification in cardiomyocytes we have generated cardiac-specific UFM1-knockout (UFM1CKO) mice. The UFM1CKO mice developed dilated cardiomyopathy at resting condition, as indicated by the left ventricle (LV) wall thinning, chamber dilatation, and impaired contractility at 4 months of age, which were further exacerbated by 6 months. It appears that UFM1 modification constrains pathological cardiac remodeling by maintaining ER homeostasis and regulating ER stress response. To test the hypothesis that UFM1 modification, instead of UFM1 itself is required to maintain cardiac function, we replenished UFM1CKO mice with cardiac-specific WT or conjugation-deficient UFM1 via AAV9. By echocardiography, we revealed that, unlike WT UFM1, overexpression of the conjugation-deficient mutant failed to attenuate the cardiac remodeling and dysfunction of the UFM1CKO heart. Interestingly, the conjugation-deficient mutant further exacerbated the cardiac dysfunction of the UFM1CKO mice. Extensive fibrosis and upregulation of ER stress response protein were also noted in conjugation-deficient mutant UFM1 injected UFM1CKO heart. Overall this study indicates that modification of proteins by UFM1 is critical to cardiac function via maintaining ER homeostasis.

Abstract Tu087: Knockout of TIGAR Rescues Cardiac Dysfunction in SIRT3 Knockout Mice

Introduction: Heart failure (HF) is the leading cause of death in the United States, despite advances in treatment, it maintains the highest disease mortality rate in the country. Previously it has been established that Sirtuin 3 (SIRT3), a mitochondrial NAD+- dependent deacetylase, and the Tp53-induced glycolysis and apoptosis regulator (TIGAR) are associated with the development of HF. SIRT3 plays a key role in the maintenance of cardiac function. Decreases in SIRT3 are associated with human aging and diabetes, whereas knockout results in cardiac dysfunction in mice. We have shown: (1) overexpression of SIRT3 downregulates TIGAR and attenuates diabetic cardiomyopathy; (2) knockout of TIGAR enhances myocardial glycolysis and reduces pathological remodeling while maintaining cardiac function in pressure-overload-induced heart failure. To date, the direct interactions between TIGAR and SIRT3 in the development of HF remain unexplored. Aim: By crossing TIGAR knockout mice (TIGARKO) with SIRT3 knockout (SIRT3KO) mice, this study tested if genetic targeting of TIGAR could rescue cardiac dysfunction in SIRT3KO mice. Methods and Results: Echocardiography was performed on SIRT3KO, TIGARKO, TIGARKO/SIRT3KO, and SIRT3 Control mice. Analysis of cardiac function showed that SIRT3KO mice had significant decreases in coronary flow reserve (CFR), ejection fraction (EF) SIRT3KO (41.52 ± 4.50) vs SIRT3 Control (60.91 ± 4.91, p<0.001) and fractional shortening (FS) SIRT3KO (20.11 ± 2.48) vs SIRT3 Control (32.07 ± 3.37, p<0.001). The diastolic E’/A’ ratio was decreased; IVRT and MPI were significantly increased. Knockout of TIGAR in mice maintained systolic function by increasing EF (62.25 ± 9.84) vs (41.52 ± 4.50, p<0.001), FS (33.33 ± 7.12 vs 20.11 ± 2.48, p<0.05), and CFR, as well as improved diastolic function by decreasing IVRT, MPI, and increasing E’/A’ ratio in SIRT3KO mice. SIRT3KO and TIGARKO mice had a significant increase in weight/tibia length ratio (HW/TL). Interestingly, the knockout of TIGAR significantly reduced LV mass and HW/TL in SIRT3KO mice. Conclusions: The knockout of TIGAR can rescue the HF phenotype of SIRT3KO mice, but the underlying mechanisms require further investigation to develop potential treatments for HF.

Abstract Tu142: Pannexin-2 Deficiency Exacerbates Stress-induced Cell Injury in Cardiomyocytes

Pannexins are a family of channel proteins involved in a variety of biological processes, including cell death signaling and immune functions. While Pannexin isoforms 1 and 3 have been widely studied, mainly in the brain, much less is known about the role of isoform 2 (Pannexin2, or Panx2). A recent study showed that deficiency in Panx2 sensitizes pancreatic beta cells to cytokine-induced apoptosis, while another study revealed that Panx2 promotes ultraviolet-induced apoptosis in keratinocytes. The role of Panx2 in the regulation of cardiomyocyte function has not been investigated. In the current study, we explored the subcellular distribution profile of Panx2 expression in cardiomyocytes (AC16 cells and adult cardiomyocytes) and examined the role of Panx2 in regulating cardiomyocyte response to stress. Western blotting analysis revealed palmitoylation of Panx2 in the heart, suggesting that this channel is located intracellularly, instead of in the plasma membrane. Confocal imaging revealed that Panx2 expression is in the proximity of the sarcoplasmic reticulum and mitochondria, confirming its intracellular localization. The stress test results indicated that the knockdown of Panx2 by siRNA exacerbated FCCP-reduced oxidative stress and cell injury in AC16 cells. Similarly, adult cardiomyocytes isolated from Panx2-KO mice were more vulnerable to ischemia-reperfusion injury compared with wild-type cells. Finally, we found that the level of Panx2 expression altered in the cardiac tissue of a mouse model with pressure overload-induced heart failure, implying that Panx2 may be involved in the pathological remodeling of a failing heart.

Advanced myocardial deformation echocardiography for evaluation of the athlete's heart: Functional and mechanistic analysis

BackgroundAssessment of the athlete's heart is challenging because of a phenotypic overlap between reactive physiological adaptation and pathological remodelling. The potential value of myocardial deformation remains controversial in identifying early cardiomyopathy. AimTo identify the echocardiographic phenotype of athletes using advanced two-dimensional speckle tracking imaging, and to define predictive factors of subtle left ventricular systolic dysfunction. MethodsIn total, 191 healthy male athletes who underwent a preparticipation medical evaluation at Nancy University Hospital between 2013 and 2020 were included. Clinical and echocardiographic data were compared with 161 healthy male subjects from the STANISLAS cohort. Borderline global longitudinal strain value was defined as<17.5%. ResultsAthletes demonstrated lower left ventricular ejection fraction (57.9±5.3% vs. 62.6±6.4%; P<0.01) and lower global longitudinal strain (17.5±2.2% vs. 21.1±2.1%; P<0.01). No significant differences were found between athletes with and without a borderline global longitudinal strain value regarding clinical characteristics, structural echocardiographic features and exercise capacity. A borderline global longitudinal strain value was associated with a lower endocardial global longitudinal strain (18.8±1.2% vs. 22.7±1.9%; P=0.02), a lower epicardial global longitudinal strain (14.0±1.1% vs. 16.6±1.2%; P<0.01) and a higher endocardial/epicardial global longitudinal strain ratio (1.36±0.07 vs. 1.32±0.06; P<0.01). No significant difference was found regarding mechanical dispersion (P=0.46). ConclusionsBorderline global longitudinal strain value in athletes does not appear to be related to structural remodelling, mechanical dispersion or exercise capacity. The athlete's heart is characterized by a specific myocardial deformation pattern with a more pronounced epicardial layer strain impairment.

Airway extracellular LTA4H concentrations are governed by release from liver hepatocytes and changes in lung vascular permeability

Leukotriene A4 hydrolase (LTA4H) is a bifunctional enzyme, with dual activities critical in defining the scale of tissue inflammation and pathology. LTA4H classically operates intracellularly, primarily within myeloid cells, to generate pro-inflammatory leukotriene B4. However, LTA4H also operates extracellularly to degrade the bioactive collagen fragment proline-glycine-proline to limit neutrophilic inflammation and pathological tissue remodeling. While the dichotomous functions of LTA4H are dictated by location, the cellular source of extracellular enzyme remains unknown. We demonstrate that airway extracellular LTA4H concentrations are governed by the level of pulmonary vascular permeability and influx of an abundant repository of blood-borne enzyme. In turn, blood LTA4H originates from liver hepatocytes, being released constitutively but further upregulated during an acute phase response. These findings have implications for our understanding of how inflammation and repair are regulated and how perturbations to the LTA4H axis may manifest in pathologies of chronic diseases.

Loss of Smooth Muscle Tenascin-X Inhibits Vascular Remodeling Through Increased TGF-β Signaling.

Vascular smooth muscle cells (VSMCs) are highly plastic. Vessel injury induces a phenotypic transformation from differentiated to dedifferentiated VSMCs, which involves reduced expression of contractile proteins and increased production of extracellular matrix and inflammatory cytokines. This transition plays an important role in several cardiovascular diseases such as atherosclerosis, hypertension, and aortic aneurysm. TGF-β (transforming growth factor-β) is critical for VSMC differentiation and to counterbalance the effect of dedifferentiating factors. However, the mechanisms controlling TGF-β activity and VSMC phenotypic regulation under in vivo conditions are poorly understood. The extracellular matrix protein TN-X (tenascin-X) has recently been shown to bind TGF-β and to prevent it from activating its receptor. We studied the role of TN-X in VSMCs in various murine disease models using tamoxifen-inducible SMC-specific knockout and adeno-associated virus-mediated knockdown. In hypertensive and high-fat diet-fed mice, after carotid artery ligation as well as in human aneurysmal aortae, expression of Tnxb, the gene encoding TN-X, was increased in VSMCs. Mice with smooth muscle cell-specific loss of TN-X (SMC-Tnxb-KO) showed increased TGF-β signaling in VSMCs, as well as upregulated expression of VSMC differentiation marker genes during vascular remodeling compared with controls. SMC-specific TN-X deficiency decreased neointima formation after carotid artery ligation and reduced vessel wall thickening during Ang II (angiotensin II)-induced hypertension. SMC-Tnxb-KO mice lacking ApoE showed reduced atherosclerosis and Ang II-induced aneurysm formation under high-fat diet. Adeno-associated virus-mediated SMC-specific expression of short hairpin RNA against Tnxb showed similar beneficial effects. Treatment with an anti-TGF-β antibody or additional SMC-specific loss of the TGF-β receptor reverted the effects of SMC-specific TN-X deficiency. In summary, TN-X critically regulates VSMC plasticity during vascular injury by inhibiting TGF-β signaling. Our data indicate that inhibition of vascular smooth muscle TN-X may represent a strategy to prevent and treat pathological vascular remodeling.

Serum Response Factor Expression in Excess Permits a Dual Contractile-Proliferative Phenotype of Airway Smooth Muscle.

The transcription factors (TFs) MyoCD (myocardin) and Elk-1 (ETS Like-1 protein) competitively bind to SRF (serum response factor) and control myogenic- and mitogenic-related gene expression in smooth muscle, respectively. Their functions are therefore mutually inhibitory, which results in a contractile-versus-proliferative phenotype dichotomy. Airway smooth muscle cell (ASMC) phenotype alterations occur in various inflammatory airway diseases, promoting pathological remodeling and contributing to airflow obstruction. We characterized MyoCD and Elk-1 interactions and their roles in phenotype determination in human ASMCs. MyoCD overexpression in ASMCs increased smooth muscle gene expression, force generation, and partially restored the loss of smooth muscle protein associated with prolonged culturing while inhibiting Elk-1 transcriptional activities and proliferation induced by EGF (epidermal growth factor). However, MyoCD overexpression failed to suppress these responses induced by FBS, as FBS also upregulated SRF expression to a degree that allowed unopposed function of both TFs. Inhibition of the RhoA pathway reversed said SRF changes, allowing inhibition of Elk-1 by MyoCD overexpression and suppressing FBS-mediated contractile protein gene upregulation. Our study confirmed that MyoCD in increased abundance can competitively inhibit Elk-1 function. However, SRF upregulation permits a dual contractile-proliferative ASMC phenotype that is anticipated to exacerbate pathological alterations, whereas therapies targeting SRF may inhibit pathological ASMC proliferation and contractile protein gene expression.

Distinct functional and molecular profiles between physiological and pathological atrial enlargement offer potential new therapeutic opportunities for atrial fibrillation.

Atrial fibrillation (AF) remains challenging to prevent and treat. A key feature of AF is atrial enlargement. However, not all atrial enlargement progresses to AF. Atrial enlargement in response to physiological stimuli such as exercise is typically benign and reversible. Understanding the differences in atrial function and molecular profile underpinning pathological and physiological atrial remodelling will be critical for identifying new strategies for AF. The discovery of molecular mechanisms responsible for pathological and physiological ventricular hypertrophy has uncovered new drug targets for heart failure. Studies in the atria have been limited in comparison. Here, we characterised mouse atria from (1) a pathological model (cardiomyocyte-specific transgenic (Tg) that develops dilated cardiomyopathy [DCM] and AF due to reduced protective signalling [PI3K]; DCM-dnPI3K), and (2) a physiological model (cardiomyocyte-specific Tg with an enlarged heart due to increased insulin-like growth factor 1 receptor; IGF1R). Both models presented with an increase in atrial mass, but displayed distinct functional, cellular, histological and molecular phenotypes. Atrial enlargement in the DCM-dnPI3K Tg, but not IGF1R Tg, was associated with atrial dysfunction, fibrosis and a heart failure gene expression pattern. Atrial proteomics identified protein networks related to cardiac contractility, sarcomere assembly, metabolism, mitochondria, and extracellular matrix which were differentially regulated in the models; many co-identified in atrial proteomics data sets from human AF. In summary, physiological and pathological atrial enlargement are associated with distinct features, and the proteomic dataset provides a resource to study potential new regulators of atrial biology and function, drug targets and biomarkers for AF.

Systemic aging fuels heart failure: Molecular mechanisms and therapeutic avenues.

Systemic aging influences various physiological processes and contributes to structural and functional decline in cardiac tissue. These alterations include an increased incidence of left ventricular hypertrophy, a decline in left ventricular diastolic function, left atrial dilation, atrial fibrillation, myocardial fibrosis and cardiac amyloidosis, elevating susceptibility to chronic heart failure (HF) in the elderly. Age-related cardiac dysfunction stems from prolonged exposure to genomic, epigenetic, oxidative, autophagic, inflammatory and regenerative stresses, along with the accumulation of senescent cells. Concurrently, age-related structural and functional changes in the vascular system, attributed to endothelial dysfunction, arterial stiffness, impaired angiogenesis, oxidative stress and inflammation, impose additional strain on the heart. Dysregulated mechanosignalling and impaired nitric oxide signalling play critical roles in the age-related vascular dysfunction associated with HF. Metabolic aging drives intricate shifts in glucose and lipid metabolism, leading to insulin resistance, mitochondrial dysfunction and lipid accumulation within cardiomyocytes. These alterations contribute to cardiac hypertrophy, fibrosis and impaired contractility, ultimately propelling HF. Systemic low-grade chronic inflammation, in conjunction with the senescence-associated secretory phenotype, aggravates cardiac dysfunction with age by promoting immune cell infiltration into the myocardium, fostering HF. This is further exacerbated by age-related comorbidities like coronary artery disease (CAD), atherosclerosis, hypertension, obesity, diabetes and chronic kidney disease (CKD). CAD and atherosclerosis induce myocardial ischaemia and adverse remodelling, while hypertension contributes to cardiac hypertrophy and fibrosis. Obesity-associated insulin resistance, inflammation and dyslipidaemia create a profibrotic cardiac environment, whereas diabetes-related metabolic disturbances further impair cardiac function. CKD-related fluid overload, electrolyte imbalances and uraemic toxins exacerbate HF through systemic inflammation and neurohormonal renin-angiotensin-aldosterone system (RAAS) activation. Recognizing aging as a modifiable process has opened avenues to target systemic aging in HF through both lifestyle interventions and therapeutics. Exercise, known for its antioxidant effects, can partly reverse pathological cardiac remodelling in the elderly by countering processes linked to age-related chronic HF, such as mitochondrial dysfunction, inflammation, senescence and declining cardiomyocyte regeneration. Dietary interventions such as plant-based and ketogenic diets, caloric restriction and macronutrient supplementation are instrumental in maintaining energy balance, reducing adiposity and addressing micronutrient and macronutrient imbalances associated with age-related HF. Therapeutic advancements targeting systemic aging in HF are underway. Key approaches include senomorphics and senolytics to limit senescence, antioxidants targeting mitochondrial stress, anti-inflammatory drugs like interleukin (IL)-1β inhibitors, metabolic rejuvenators such as nicotinamide riboside, resveratrol and sirtuin (SIRT) activators and autophagy enhancers like metformin and sodium-glucose cotransporter 2 (SGLT2) inhibitors, all of which offer potential for preserving cardiac function and alleviating the age-related HF burden.

Design, Synthesis, and Evaluation of the Selective and Orally Active LSD1 Inhibitor with the Potential of Treating Heart Failure.

LSD1 has become an appealing target for the development of new pharmacologic agents to treat cardiovascular diseases, including heart failure. Herein, we reported the design, synthesis, and structure-activity relationship of a series of TCP-based derivatives targeting LSD1. Docking studies were employed to successfully elucidate the SAR. Particularly, compound 7d, characterized by low toxicity, demonstrated a high affinity for LSD1 at molecular and cellular levels. It also displayed favorable pharmacokinetic properties for oral dosing (e.g., F = 77.61%), effectively alleviating Ang II-induced NRCFs activation in vitro and reducing pathological myocardial remodeling in TAC-induced cardiac remodeling and heart failure in vivo. Additionally, mechanism studies revealed that suppression of myocardial dysfunction by compound 7d is related to LSD1 inhibition-induced TGFβ signaling pathway repressing. In summary, the current report presents compound 7d as a potent LSD1 inhibitor with the potential for further development as a therapeutic agent for pressure overload-related heart failure.

Diastolic dysfunction in Alzheimer’s disease model mice is associated with Aβ-amyloid aggregate formation and mitochondrial dysfunction

Alzheimer's Disease (AD) is a progressive neurodegenerative disease caused by the deposition of Aβ aggregates or neurofibrillary tangles. AD patients are primarily diagnosed with the concurrent development of several cardiovascular dysfunctions. While few studies have indicated the presence of intramyocardial Aβ aggregates, none of the studies have performed detailed analyses for pathomechanism of cardiac dysfunction in AD patients. This manuscript used aged APPSWE/PS1 Tg and littermate age-matched wildtype (Wt) mice to characterize cardiac dysfunction and analyze associated pathophysiology. Detailed assessment of cardiac functional parameters demonstrated the development of diastolic dysfunction in APPSWE/PS1 Tg hearts compared to Wt hearts. Muscle function evaluation showed functional impairment (decreased exercise tolerance and muscle strength) in APPSWE/PS1 Tg mice. Biochemical and histochemical analysis revealed Aβ aggregate accumulation in APPSWE/PS1 Tg mice myocardium. APPSWE/PS1 Tg mice hearts also demonstrated histopathological remodeling (increased collagen deposition and myocyte cross-sectional area). Additionally, APPSWE/PS1 Tg hearts showed altered mitochondrial dynamics, reduced antioxidant protein levels, and impaired mitochondrial proteostasis compared to Wt mice. APPSWE/PS1 Tg hearts also developed mitochondrial dysfunction with decreased OXPHOS and PDH protein complex expressions, altered ETC complex dynamics, decreased complex activities, and reduced mitochondrial respiration. Our results indicated that Aβ aggregates in APPSWE/PS1 Tg hearts are associated with defects in mitochondrial respiration and complex activities, which may collectively lead to cardiac diastolic dysfunction and myocardial pathological remodeling.

Glucagon Receptor Antagonist for Heart Failure With Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is an emerging major unmet need and one of the most significant clinic challenges in cardiology. The pathogenesis of HFpEF is associated with multiple risk factors. Hypertension and metabolic disorders associated with obesity are the 2 most prominent comorbidities observed in patients with HFpEF. Although hypertension-induced mechanical overload has long been recognized as a potent contributor to heart failure with reduced ejection fraction, the synergistic interaction between mechanical overload and metabolic disorders in the pathogenesis of HFpEF remains poorly characterized. We investigated the functional outcome and the underlying mechanisms from concurrent mechanic and metabolic stresses in the heart by applying transverse aortic constriction in lean C57Bl/6J or obese/diabetic B6.Cg-Lepob/J (ob/ob) mice, followed by single-nuclei RNA-seq and targeted manipulation of a top-ranked signaling pathway differentially affected in the 2 experimental cohorts. In contrast to the post-transverse aortic constriction C57Bl/6J lean mice, which developed pathological features of heart failure with reduced ejection fraction over time, the post-transverse aortic constriction ob/ob mice showed no significant changes in ejection fraction but developed characteristic pathological features of HFpEF, including diastolic dysfunction, worsened cardiac hypertrophy, and pathological remodeling, along with further deterioration of exercise intolerance. Single-nuclei RNA-seq analysis revealed significant transcriptome reprogramming in the cardiomyocytes stressed by both pressure overload and obesity/diabetes, markedly distinct from the cardiomyocytes singularly stressed by pressure overload or obesity/diabetes. Furthermore, glucagon signaling was identified as the top-ranked signaling pathway affected in the cardiomyocytes associated with HFpEF. Treatment with a glucagon receptor antagonist significantly ameliorated the progression of HFpEF-related pathological features in 2 independent preclinical models. Importantly, cardiomyocyte-specific genetic deletion of the glucagon receptor also significantly improved cardiac function in response to pressure overload and metabolic stress. These findings identify glucagon receptor signaling in cardiomyocytes as a critical determinant of HFpEF progression and provide proof-of-concept support for glucagon receptor antagonism as a potential therapy for the disease.

Understanding the roles of salt-inducible kinases in cardiometabolic disease.

Salt-inducible kinases (SIKs) are serine/threonine kinases of the adenosine monophosphate-activated protein kinase family. Acting as mediators of a broad array of neuronal and hormonal signaling pathways, SIKs play diverse roles in many physiological and pathological processes. Phosphorylation by the upstream kinase liver kinase B1 is required for SIK activation, while phosphorylation by protein kinase A induces the binding of 14-3-3 protein and leads to SIK inhibition. SIKs are subjected to auto-phosphorylation regulation and their activity can also be modulated by Ca2+/calmodulin-dependent protein kinase in response to cellular calcium influx. SIKs regulate the physiological processes through direct phosphorylation on various substrates, which include class IIa histone deacetylases, cAMP-regulated transcriptional coactivators, phosphatase methylesterase-1, among others. Accumulative body of studies have demonstrated that SIKs are important regulators of the cardiovascular system, including early works establishing their roles in sodium sensing and vascular homeostasis and recent progress in pulmonary arterial hypertension and pathological cardiac remodeling. SIKs also regulate inflammation, fibrosis, and metabolic homeostasis, which are essential pathological underpinnings of cardiovascular disease. The development of small molecule SIK inhibitors provides the translational opportunity to explore their potential as therapeutic targets for treating cardiometabolic disease in the future.

Epigenetic Alteration of Smooth Muscle Cells Regulates Endothelin-Dependent Blood Pressure and Hypertensive Arterial Remodeling.

Long-standing hypertension (HTN) affects multiple organ systems and leads to pathologic arterial remodeling, which is driven largely by smooth muscle cell (SMC) plasticity. Although genome wide association studies (GWAS) have identified numerous variants associated with changes in blood pressure in humans, only a small percentage of these variants actually cause HTN. In order to identify relevant genes important in SMC function in HTN, we screened three separate human GWAS and Mendelian randomization studies to identify SNPs located within non-coding gene regions, focusing on genes encoding epigenetic enzymes, as these have been recently identified to control SMC fate in cardiovascular disease. We identified SNPs rs62059712 and rs74480102 in the promoter of the human JMJD3 gene and show that the minor C allele increases JMJD3 transcription in SMCs via increased SP1 binding to the JMJD3 promoter. Using our novel SMC-specific Jmjd3-deficient murine model ( Jmjd3 flox/flox Myh11 CreERT ), we show that loss of Jmjd3 in SMCs results in HTN, mechanistically, due to decreased EDNRB expression and a compensatory increase in EDNRA expression. As a translational corollary, through single cell RNA-sequencing (scRNA-seq) of human arteries, we found strong correlation between JMJD3 and EDNRB expression in SMCs. Further, we identified that JMJD3 is required for SMC-specific gene expression, and loss of JMJD3 in SMCs in the setting of HTN results in increased arterial remodeling by promoting the SMC synthetic phenotype. Our findings link a HTN-associated human DNA variant with regulation of SMC plasticity, revealing therapeutic targets that may be used in the screening and/or personalized treatment of HTN.

Targeted H2S-Mediated Gas Therapy with pH-Sensitive Release Property for Myocardial Ischemia-Reperfusion Injury by Platelet Membrane.

Management of myocardial ischemia-reperfusion injury (MIRI) in reperfusion therapy remains a major obstacle in the field of cardiovascular disease, but current available therapies have not yet been achieved in mitigating myocardial injury due to the complex pathological mechanisms of MIRI. Exogenous delivery of hydrogen sulfide (H2S) to the injured myocardium can be an effective strategy for treating MIRI due to the multiple physiologic functions of H2S, including anti-inflammatory, anti-apoptotic, and mitochondrial protective effects. Here, to realize the precise delivery and release of H2S, we proposed the targeted H2S-mediated gas therapy with pH-sensitive release property mediated by platelet membranes (PMs). In this study, a biomimetic functional poly(lactic-co-ethanolic acid) nanoparticle (RAPA/JK-1-PLGA@PM) was fabricated by loading rapamycin (RAPA; mTOR inhibitor) and JK-1 (H2S donor) and then coated with PM. Invitro observations were conducted including pharmaceutical evaluation, H2S release behaviors, hemolysis analysis, serum stability, cellular uptake, cytotoxicity, inhibition of myocardial apoptosis, and anti-inflammation. Invivo examinations were performed including targeting ability, restoration of cardiac function, inhibition of pathological remodeling, and anti-inflammation. RAPA/JK-1-PLGA@PM was successfully prepared with good size distribution and stability. Utilizing the natural infarct-homing ability of PM, RAPA/JK-1-PLGA@PM could be effectively targeted to the damaged myocardium. RAPA/JK-1-PLGA@PM continuously released H2S triggered by inflammatory microenvironment, which could inhibit cardiomyocyte apoptosis, realize the transition of pro-inflammation, and alleviate myocardial injury demonstrated in hypoxia/reoxygenation myocardial cell invitro. Precise delivery and release of H2S attenuated inflammatory response and cardiac damage, promoted cardiac repair, and ameliorated cardiac function proven in MIRI mouse model invivo. This research outlined the novel nanoplatform that combined immunosuppressant agents and H2S donor with the pH-sensitive release property, offering a promising therapeutic for MIRI treatment that leveraged the synergistic effects of gas therapy.

Insulin-like growth factor-binding protein 7 (IGFBP7): A microenvironment-dependent regulator of angiogenesis and vascular remodeling.

Insulin-like Growth Factor-Binding Protein 7 (IGFBP7) is an extracellular matrix (ECM) glycoprotein, highly enriched in activated vasculature during development, physiological and pathological tissue remodeling. Despite decades of research, its role in tissue (re-)vascularization is highly ambiguous, exhibiting pro- and anti-angiogenic properties in different tissue remodeling states. IGFBP7 has multiple binding partners, including structural ECM components, cytokines, chemokines, as well as several receptors. Based on current evidence, it is suggested that IGFBP7's bioactivity is strongly dependent on the microenvironment it is embedded in. Current studies indicate that during physiological angiogenesis, IGFBP7 promotes endothelial cell attachment, luminogenesis, vessel stabilization and maturation. Its effects on other stages of angiogenesis and vessel function remain to be determined. IGFBP7 also modulates the pro-angiogenic properties of other signaling factors, such as VEGF-A and IGF, and potentially acts as a growth factor reservoir, while its actual effects on the factors' signaling may depend on the environment IGFBP7 is embedded in. Besides (re-)vascularization, IGFBP7 clearly promotes progenitor and stem cell commitment and may exhibit anti-inflammatory and anti-fibrotic properties. Nonetheless, its role in inflammation, immunomodulation, fibrosis and cellular senescence is again likely to be context-dependent. Future studies are required to shed more light on the intricate functioning of IGFBP7.

Transcriptional coactivation of NRF2 signaling in cardiac fibroblasts promotes resistance to oxidative stress

We recently discovered that steroid receptor coactivators (SRCs) SRCs-1, 2 and 3, are abundantly expressed in cardiac fibroblasts (CFs) and their activation with the SRC small molecule stimulator MCB-613 improves cardiac function and dramatically lowers pro-fibrotic signaling in CFs post-myocardial infarction. These findings suggest that CF-derived SRC activation could be beneficial in the mitigation of chronic heart failure after ischemic insult. However, the cardioprotective mechanisms by which CFs contribute to cardiac pathological remodeling are unclear. Here we present studies designed to identify the molecular and cellular circuitry that governs the anti-fibrotic effects of an MCB-613 derivative, MCB-613-10-1, in CFs. We performed cytokine profiling and whole transcriptome and proteome analyses of CF-derived signals in response to MCB-613-10-1. We identified the NRF2 pathway as a direct MCB-613-10-1 therapeutic target for promoting resistance to oxidative stress in CFs. We show that MCB-613-10-1 promotes cell survival of anti-fibrotic CFs exposed to oxidative stress by suppressing apoptosis. We demonstrate that an increase in HMOX1 expression contributes to CF resistance to oxidative stress-mediated apoptosis via a mechanism involving SRC co-activation of NRF2, hence reducing inflammation and fibrosis. We provide evidence that MCB-613-10-1 acts as a protectant against oxidative stress-induced mitochondrial damage. Our data reveal that SRC stimulation of the NRF2 transcriptional network promotes resistance to oxidative stress and highlights a mechanistic approach toward addressing pathologic cardiac remodeling.

Structural phenotyping in atrial fibrillation with combined cardiac CT and atrial MRI: Identifying and differentiating individual structural remodelling types in AF.

Atrial remodelling (AR) is the persistent change in atrial structure and/or function and contributes to the initiation, maintenance and progression of atrial fibrillation (AF) in a reciprocal self-perpetuating relationship. Left atrial (LA) size, geometry, fibrosis, wall thickness (LAWT) and ejection fraction (LAEF) have all been shown to vary with pathological atrial remodelling. The association of these global remodelling markers with each other for differentiating structural phenotypes in AF is not well investigated. Patients referred for first-time AF ablation and controls without AF were prospectively recruited to undergo cardiac computed tomographic angiography (CCTA) and magnetic resonance imaging (MRI) with 3D atrial late-gadolinium enhanced (LGE) sequences. LAWT, atrial myocardial mass, LA volume and sphericity were calculated from CT. Biplane LA EF and LA fibrosis burden were derived from atrial MRI. Results were compared between patients with AF and controls. Forty two AF patients (64.3% male, age 64.6 ± 10.2 years, CHA2DS2-VASc 2.48 ± 1.5, 69.0% paroxysmal AF, 31% persistent AF, LVEF 57.9 ± 10.5%) and 37 controls (64.9% male, age 56.6 ± 7.2, CHA2DS2-VASc 1.54 ± 1.1, LVEF 60.4 ± 4.9%) were recruited. Patients with AF had a significantly higher LAWT (1.45 ± 0.52 mm vs 1.12 ± 0.42 mm, p = 0.003), tissue mass (15.81 ± 6.53 g vs. 12.18 ± 5.01 g, p = 0.011), fibrosis burden (9.33 ± 8.35% vs 2.41 ± 3.60%, p = 0.013), left atrial size/volume (95.68 ± 26.63 mL vs 81.22 ± 20.64 mL, p = 0.011) and lower LAEF (50.3 ± 15.3% vs 65.2 ± 8.6%, p < 0.001) compared to controls. There was no significant correlation between % fibrosis with LAWT (p = 0.29), mass (p = 0.89), volume (p = 0.49) or sphericity (p = 0.79). LAWT had a statistically significant weak positive correlation with LA volume (r = 0.25, p = .041), but not with sphericity (p = 0.86). LAEF had a statistically significant but weak negative correlation with fibrosis (r = -0.33, p = 0.008) and LAWT (r = -0.24, p = 0.07). AF is associated with significant quantifiable structural changes that are evident in LA size, tissue thickness, total LA tissue mass and fibrosis. These individual remodelling markers do not or only weakly correlate with each other suggesting different remodelling subtypes exist (e.g. fibrotic vs hypertrophic vs dilated). If confirmed, such a detailed understanding of the structural changes observed has the potential to inform clinical management strategies targeting individual mechanisms underlying the disease process.