The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Systemic inflammation is associated with myocardial fibrosis in patients with obstructive hypertrophic cardiomyopathy

AIMS

Chronic low-grade inflammation, often observed in hypertrophic cardiomyopathy (HCM), promotes adverse ventricular remodelling. This study aimed to investigate the relationship between inflammatory markers and myocardial fibrosis (MF) in patients with HCM.

METHODS AND RESULTS

This study included 102 patients with complete baseline data who underwent septal myectomy. Myocardial samples were stained with Masson's trichrome and analysed to determine myocardial collagen content and MF levels. Plasma levels of inflammatory markers were measured using standard laboratory procedures. Univariate and multivariate logistic regression analyses were performed to explore the relationship between the inflammatory markers and MF. Among the 102 participants included in the analysis, the mean age was 48.9 years, with 69 [67.6%] being men. The overall MF ranged from 2.5% to 40.7% (mean = 15.2 ± 8.1%, median = 13.0%, IQR = 9.9%-18.4%). Participants were divided into two groups based on a median MF of 13%. The high MF group had a larger left atrial diameter and left ventricular ejection fraction. Levels of interleukin (IL)-2, tumour necrosis factor (TNF)-α and interferon (IFN)-α were significantly higher in patients with high MF compared to those with low MF (2.3 vs. 4.0 pg/mL, 3.1 vs. 3.9 pg/mL, 4.2 vs.4.7 pg/mL, respectively; all P < 0.05). In multivariate models adjusted for age, sex and other clinical features, IL-2, IL-5 and TNF-α, were correlated with increased interstitial MF [odds ratio (OR): 1.54, 95% confidence interval (CI): 1.10-2.14; OR: 1.42, 95% CI: 1.02-1.98; OR: 1.33, 95% CI: 1.04-1.70]. After additional adjustment for imaging indicators, IL-2 and TNF-α remained significant (OR: 1.49, 95% CI: 1.06-2.09, P = 0.021; OR:1.35, 95% CI: 1.01-1.80, P = 0.044). The correlation analysis between inflammation and replacement fibrosis assessed by CMR in 97 patients revealed that 72 (74.2%) showed late gadolinium enhancement (LGE). No significant correlation was found between inflammatory markers and the presence or extent of LGE.

CONCLUSIONS

Higher levels of IL-2 and TNF-α were associated with increased histopathological interstitial MF in patients with HCM. Given the gradual progression of MF in HCM, initiating anti-inflammatory treatment in the early stages may delay its progression.

Chronic cold exposure causes left ventricular hypertrophy that appears to be physiological

Exposure to winter cold causes an increase in energy demands to meet the challenge of thermoregulation. In small rodents, this increase in cardiac output leads to a profound cardiac hypertrophy, 2-3 times that typically seen with exercise training. The nature of this hypertrophy and its relevance to winter mortality remains unclear. Our goal was to characterize cold-induced cardiac hypertrophy and to assess its similarity to either exercise-induced (physiological) hypertrophy or the pathological hypertrophy of hypertension. We hypothesized that cold-induced hypertrophy will most closely resemble exercise-induced hypertrophy, but be another unique pathway for physiological cardiac growth. We found that cold-induced hypertrophy was largely reversed after a return to warm temperatures. Further, metabolic rates were elevated while gene expression and mitochondrial enzyme activities indicative of pathology were absent. A gene expression panel comparing hearts of exercised and cold-exposed mice further suggests that these activities are similar, although not identical. In conclusion, we found that chronic cold led to a phenotype that most closely resembled physiological hypertrophy, with enhanced metabolic rate, without induction of fetal genes, but with decreased expression of genes associated with fatty acid oxidation, suggesting that heart failure is not a cause of winter mortality in small rodents and identifying a novel approach for the study of cardiac growth.

Exploring PKG signaling as a therapeutic avenue for pressure overload, ischemia, and HFpEF

INTRODUCTION

Heart failure (HF) is a complex and heterogeneous syndrome resulting from any diastolic or systolic dysfunction of the cardiac muscle. In addition to comorbid conditions, pressure overload, and myocardial ischemia are associated with cardiac remodeling which manifests as extracellular matrix (ECM) perturbations, impaired cellular responses, and subsequent ventricular dysfunction.

AREAS COVERED

The current review discusses the main aspects of the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway (cGMP-PKG) pathway modulators and highlights the promising outcomes of its novel pharmacological boosters.

EXPERT OPINION

Among several signaling pathways involved in the pathogenesis of pressure overload, ischemia and HF with preserved ejection fraction (HFpEF) is cGMP-PKG pathway. This pathway plays a pivotal role in the regulation of cardiac contractility, and modulation of cGMP-PKG signaling, contributing to the development of the diseases. Ventricular cardiomyocytes of HF patients and animal models are known to exhibit reduced cGMP levels and disturbed cGMP signaling including hypophosphorylation of PKG downstream targets. However, restoration of cGMP-PKG signaling improves cardiomyocyte function and promotes cardioprotective effects.

Magnoflorine attenuates Ang II-induced cardiac remodeling via promoting AMPK-regulated autophagy

Background

Heart failure (HF) remains one of the most common events in the progression of hypertension. Magnoflorine (MNF) has been shown beneficial effects on the cardiovascular system. However, the action of MNF on angiotensin (Ang) II-induced cardiac remodeling and its underlying mechanisms have not yet been characterised. Here, we assessed the action of MNF in the development of hypertension-related HF.

Methods

C57BL/6 male mice were subjected to Ang II through a micro-osmotic pump infusion continuously for 4 weeks to induce hypertensive HF. MNF (10 and 20 mg/kg) was administered in the final 2 weeks. Ang II content was measured by enzyme-linked immunosorbent assay (ELISA) kit. Values of ejection fraction (EF) and fractional shortening (FS) were detected using an ultrasound diagnostic instrument. The mRNA levels of hypertrophic and fibrotic genes were determined by real-time quantitative polymerase chain reaction (RT-qPCR). Haematoxylin and eosin (H&E), wheat germ agglutinin (WGA), Masson trichrome, and Sirius Red staining were used to analyse pathologic changes in heart tissues. The expression levels of phosphorylated AMP-activated protein kinase (AMPK), light chain 3 microtubule associated protein II (LC3 II) to LC3 I, and p62 were detected by western blot assay.

Results

MNF significantly improved cardiac dysfunction and the content of creatine kinase-MB without altering blood pressure in Ang II-challenged mice. MNF obviously corrected the phenotypes of cardiac hypertrophy and fibrosis, including the high mRNA levels of atrial natriuretic peptide (Anp), brain natriuretic peptide (Bnp), collagen1a (Col1a1), transforming growth factor beta (Tgfb1), enlarged myocardial areas, and increased positive areas of Masson trichrome and Sirius Red staining. In addition, MNF alleviated oxidative injury, reflected by the upregulation of glutathione and the downregulation of reactive oxygen species and malondialdehyde. The activation of AMPK was elevated accompanied by an increased level of autophagy by MNF in hypertensive heart tissues. The therapeutic action of MNF was confirmed in Ang II-challenged H9c2 cells. Specifically, the AMPK inhibitor could eliminate the autophagy pathway in which MNF is involved.

Conclusions

MNF has benefits in hypertension-induced cardiac remodeling, which was partially associated with the improvement of oxidative stress via the mediation of the AMPK/autophagy axis.

Unlocking the Potential: Angiotensin Receptor Neprilysin and Sodium Glucose Co-Transporter 2 Inhibitors for Right Ventricle Dysfunction in Heart Failure

This review article examines the mechanism of action of Angiotensin Receptor-Neprilysin Inhibitors (ARNIs) and Sodium-Glucose Co-Transporter 2 Inhibitors (SGLT2is) in managing chronic right ventricular (RV) dysfunction. Despite advancements in heart failure (HF) treatment, RV dysfunction remains a significant contributor to morbidity and mortality. This article explores the The article explores the impact of ARNIs and SGLT2is on RV function based on clinical and preclinical evidence, and the potential benefits of combined therapy. It highlights the need for further research to optimize patient outcomes and suggests that RV function should be considered in future clinical trials as part of risk stratification for HF therapies. This review underscores the importance of the early initiation of ARNIs and SGLT2is as per guideline-directed medical therapy for eligible HFrEF and HFpEF patients to improve co-existing RV dysfunction.

Large animal models of pressure overload-induced cardiac left ventricular hypertrophy to study remodelling of the human heart with aortic stenosis

Pathologic cardiac hypertrophy is a common consequence of many cardiovascular diseases, including aortic stenosis (AS). AS is known to increase the pressure load of the left ventricle, causing a compensative response of the cardiac muscle, which progressively will lead to dilation and heart failure. At a cellular level, this corresponds to a considerable increase in the size of cardiomyocytes, known as cardiomyocyte hypertrophy, while their proliferation capacity is attenuated upon the first developmental stages. Cardiomyocytes, in order to cope with the increased workload (overload), suffer alterations in their morphology, nuclear content, energy metabolism, intracellular homeostatic mechanisms, contractile activity, and cell death mechanisms. Moreover, modifications in the cardiomyocyte niche, involving inflammation, immune infiltration, fibrosis, and angiogenesis, contribute to the subsequent events of a pathologic hypertrophic response. Considering the emerging need for a better understanding of the condition and treatment improvement, as the only available treatment option of AS consists of surgical interventions at a late stage of the disease, when the cardiac muscle state is irreversible, large animal models have been developed to mimic the human condition, to the greatest extend. Smaller animal models lack physiological, cellular and molecular mechanisms that sufficiently resemblance humans and in vitro techniques yet fail to provide adequate complexity. Animals, such as the ferret (Mustello purtorius furo), lapine (rabbit, Oryctolagus cunigulus), feline (cat, Felis catus), canine (dog, Canis lupus familiaris), ovine (sheep, Ovis aries), and porcine (pig, Sus scrofa), have contributed to research by elucidating implicated cellular and molecular mechanisms of the condition. Essential discoveries of each model are reported and discussed briefly in this review. Results of large animal experimentation could further be interpreted aiming at prevention of the disease progress or, alternatively, at regression of the implicated pathologic mechanisms to a physiologic state. This review summarizes the important aspects of the pathophysiology of LV hypertrophy and the applied surgical large animal models that currently better mimic the condition.

Combined Pharmacological Modulation of Translational and Transcriptional Activity Signaling Pathways as a Promising Therapeutic Approach in Children with Myocardial Changes

Myocardial hypertrophy is the most common condition that accompanies heart development in children. Transcriptional gene expression regulating pathways play a critical role both in cardiac embryogenesis and in the pathogenesis of congenital hypertrophic cardiomyopathy, neonatal posthypoxic myocardial hypertrophy, and congenital heart diseases. This paper describes the state of cardiac gene expression and potential pharmacological modulators at different transcriptional levels. An experimental model of perinatal cardiac hypoxia showed the downregulated expression of genes responsible for cardiac muscle integrity and overexpressed genes associated with energy metabolism and apoptosis, which may provide a basis for a therapeutic approach. Current evidence suggests that RNA drugs, theaflavin, neuraminidase, proton pumps, and histone deacetylase inhibitors are promising pharmacological agents in progressive cardiac hypertrophy. The different points of application of the above drugs make combined use possible, potentiating the effects of inhibition in specific signaling pathways. The special role of N-acetyl cysteine in both the inhibition of several signaling pathways and the reduction of oxidative stress was emphasized.

Implications for neutrophils in cardiac arrhythmias

Cardiac arrhythmias commonly occur as a result of aberrant electrical impulse formation or conduction in the myocardium. Frequently discussed triggers include underlying heart diseases such as myocardial ischemia, electrolyte imbalances, or genetic anomalies of ion channels involved in the tightly regulated cardiac action potential. Recently, the role of innate immune cells in the onset of arrhythmic events has been highlighted in numerous studies, correlating leukocyte expansion in the myocardium to increased arrhythmic burden. Here, we aim to call attention to the role of neutrophils in the pathogenesis of cardiac arrhythmias and their expansion during myocardial ischemia and infectious disease manifestation. In addition, we will elucidate molecular mechanisms associated with neutrophil activation and discuss their involvement as direct mediators of arrhythmogenicity.

Transcriptomic Analyses and Experimental Validation Identified Immune-Related lncRNA-mRNA Pair MIR210HG-BPIFC Regulating the Progression of Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a disease in which the myocardium of the heart becomes asymmetrically thickened, malformed, disordered, and loses its normal structure and function. Recent studies have demonstrated the significant involvement of inflammatory responses in HCM. However, the precise role of immune-related long non-coding RNAs (lncRNAs) in the pathogenesis of HCM remains unclear. In this study, we performed a comprehensive analysis of immune-related lncRNAs in HCM. First, transcriptomic RNA-Seq data from both HCM patients and healthy individuals (GSE180313) were reanalyzed thoroughly. Key HCM-related modules were identified using weighted gene co-expression network analysis (WGCNA). A screening for immune-related lncRNAs was conducted within the key modules using immune-related mRNA co-expression analysis. Based on lncRNA-mRNA pairs that exhibit shared regulatory microRNAs (miRNAs), we constructed a competing endogenous RNA (ceRNA) network, comprising 9 lncRNAs and 17 mRNAs that were significantly correlated. Among the 26 lncRNA-mRNA pairs, only the MIR210HG-BPIFC pair was verified by another HCM dataset (GSE130036) and the isoprenaline (ISO)-induced HCM cell model. Furthermore, knockdown of MIR210HG increased the regulatory miRNAs and decreased the mRNA expression of BPIFC correspondingly in AC16 cells. Additionally, the analysis of immune cell infiltration indicated that the MIR210HG-BPIFC pair was potentially involved in the infiltration of naïve CD4+ T cells and CD8+ T cells. Together, our findings indicate that the decreased expression of the lncRNA-mRNA pair MIR210HG-BPIFC was significantly correlated with the pathogenesis of the disease and may be involved in the immune cell infiltration in the mechanism of HCM.

Cardiac recovery from pressure overload is not altered by thyroid hormone status in old mice

Introduction

Thyroid hormones (THs) are known to have various effects on the cardiovascular system. However, the impact of TH levels on preexisting cardiac diseases is still unclear. Pressure overload due to arterial hypertension or aortic stenosis and aging are major risk factors for the development of structural and functional abnormalities and subsequent heart failure. Here, we assessed the sensitivity to altered TH levels in aged mice with maladaptive cardiac hypertrophy and cardiac dysfunction induced by transverse aortic constriction (TAC).

Methods

Mice at the age of 12 months underwent TAC and received T4 or anti-thyroid medication in drinking water over the course of 4 weeks after induction of left ventricular pressure overload.

Results

T4 excess or deprivation in older mice had no or only very little impact on cardiac function (fractional shortening), cardiac remodeling (cardiac wall thickness, heart weight, cardiomyocyte size, apoptosis, and interstitial fibrosis), and mortality. This is surprising because T4 excess or deprivation had significantly changed the outcome after TAC in young 8-week-old mice. Comparing the gene expression of deiodinases (Dio) 2 and 3 and TH receptor alpha (TRα) 1 and the dominant-negative acting isoform TRα2 between young and aged mice revealed that aged mice exhibited a higher expression of TRα2 and Dio3, while expression of Dio2 was reduced compared with young mice. These changes in Dio2 and 3 expressions might lead to reduced TH availability in the hearts of 12-month-old mice accompanied by reduced TRα action due to higher TRα2.

Discussion

In summary, our study shows that low and high TH availability have little impact on cardiac function and remodeling in older mice with preexisting pressure-induced cardiac damage. This observation seems to be the result of an altered expression of deiodinases and TRα isoforms, thus suggesting that even though cardiovascular risk is increasing with age, the response to TH stress may be dampened in certain conditions.

Pterostilbene attenuates heart failure by inhibiting myocardial ferroptosis through SIRT1/GSK-3β/GPX4 signaling pathway

Sustained myocardial injury due to hypertension and diabetes mellitus leads to production of endogenous reactive oxygen species (ROS) and insufficient myocardial antioxidant capacity, increasing the risk of cardiomyocyte ferroptosis. Ferroptosis is a nonapoptotic form of cell death driven by unrestricted lipid peroxidation. Dysfunction of the glutathione peroxidase 4 (GPX4) antioxidant system also plays an important role in ferroptosis. Cardiomyocyte ferroptosis ultimately leads to myocardial deterioration, such as inflammation, fibrosis, and cardiac remodeling, resulting in structural and functional changes. Pterostilbene (PTS), a demethylated derivative of resveratrol, exhibits strong anti-inflammatory and antioxidative activities. In this study, we used in vitro experiments to explore ferroptosis induced by angiotensin II (Ang II) of primary cardiac myocytes (CMs) and in vivo experiments to prepare a transverse aortic constriction (TAC)-induced cardiac dysfunction mouse model. PTS can significantly ameliorate Ang II-induced cardiomyocyte ferroptosis in vitro and reduce cardiac remodeling, while improving cardiac function in mice after TAC in vivo. Further mechanistic investigations revealed that PTS exerts its protective effect through the SIRT1/GSK-3β/GPX4 pathway. After siRNA-mediated knockdown of SIRT1 or GPX4 in CMs, the protective effects of PTS on cardiomyocytes were abolished. This study provides important theoretical support for the potential of PTS to attenuate pathological cardiac remodeling and heart failure and provides a preliminary exploration of the molecular pathways involved in its protective mechanism.

Discrimination models with radiomics features derived from cardiovascular magnetic resonance images for distinguishing hypertensive heart disease from hypertrophic cardiomyopathy

Background

Discriminating hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HHD) is challenging, because both are characterized by left ventricular hypertrophy (LVH). Radiomics might be effective to differentiate HHD from HCM. Therefore, this study aimed to investigate discriminators and build discrimination models between HHD and HCM using multiparametric cardiac magnetic resonance (CMR) findings and radiomics score (radscore) derived from late gadolinium enhancement (LGE) and cine images.

Methods

In this single center, retrospective study, 421 HCM patients [median and interquartile range (IQR), 50.0 (38.0-59.0) years; male, 70.5%] from January 2017 to September 2021 and 200 HHD patients [median and IQR, 44.5 (35.0-57.0) years; male, 88.5%] from September 2015 to July 2022 were consecutively included and randomly stratified into a training group and a validation group at a ratio of 6:4. Multiparametric CMR findings were obtained using cvi42 software and radiomics features using Python software. After dimensional reduction, the radscore was calculated by summing the remaining radiomics features weighted by their coefficients. Multiparametric CMR findings and radscore that were statistically significant in univariate logistic regression were used to build combined discrimination models via multivariate logistic regression.

Results

After multivariate logistic regression, the maximal left ventricular end diastolic wall thickness (LVEDWT), left ventricular ejection fraction (LVEF), presence of LGE, cine radscore and LGE radscore were identified as significant characteristics and used to build a combined discrimination model. This model achieved an area under the receiver operator characteristic curve (AUC) of 0.979 (0.968-0.990) in the training group and 0.981 (0.967-0.995) in the validation group, significantly better than the model using multiparametric CMR findings alone (P<0.001).

Conclusions

Radiomics features derived from cardiac cine and LGE images can effectively discriminate HHD from HCM.

Myocardial Angiotensin-Converting Enzyme 2 Protein Expression in Ischemic Heart Failure

The angiotensin-converting enzyme 2 (ACE2)-angiotensin-(1-7)-Mas receptor axis plays a significant role in regulating myocardial remodeling and the development of heart failure (HF), with ACE2 being the primary focus. However, contemporary understanding of the membrane-bound form of the human ACE2 protein remains insufficient. The purpose of this study was to determine the expression of ACE2 protein in different cells of the left ventricular myocardium in non-diseased hearts and at various stages of ischemic HF. A total of 103 myocardial tissue samples from the left ventricle underwent quantitative and semi-quantitative immunohistochemical analysis. Upon assessing ACE2 immunostaining in all myocardial cells through unselective digital image analysis, there was no change in the stage A HF group. Nevertheless, the expression of ACE2 membrane protein in cardiomyocytes showed a tendency to increase, while non-cardiomyocyte ACE2 expression decreased significantly (p < 0.001). In the stage B HF group, the intensity of ACE2 immunostaining continued to increase with rising cardiomyocyte ACE2 expression (p < 0.001). Non-cardiomyocyte expression, in contrast, remained similar to that observed in the stage A HF group. In the stages C/D HF group, ACE2 expression reached its highest level in cardiomyocytes (p < 0.001), while ACE2 expression in non-cardiomyocytes was the lowest (p < 0.001). These changes in ACE2 protein levels are associated with left ventricular remodeling in ischemic HF.