New Insights in Cardiac β-Adrenergic Signaling During Heart Failure and Aging

Design, synthesis, and X-ray structural studies of a series of highly potent, selective, and drug-like G protein-coupled receptor kinase 5 inhibitors

G protein-coupled receptor kinase 5 (GRK5) has emerged as a potential drug development target against heart failure and cancer. A close homolog, GRK6 represents a therapeutic target for multiple myeloma. We have rationally designed a series of highly selective, potent, noncovalent, and drug-like GRK5 inhibitors. Several inhibitors exhibited low nanomolar GRK5 inhibition and high selectivity over GRK2, and, surprisingly, some were selective for GRK6. We determined high-resolution X-ray crystal structures of several inhibitors in complex with GRK5, which provide molecular insights into the ligand-binding site interactions responsible for GRK5 selectivity and potency.

Circulating mitochondria carrying cGAS promote endothelial Secreted group IIA phospholipase A2-mediated neuroinflammation through activating astroglial/microglial Integrin-alphavbeta3 in subfornical organ to augment central sympathetic overdrive in heart failure rats

BACKGROUND

Sympathoexcitation, a manifestation of heart-brain axis dysregulation, contributes to the progression of heart failure (HF). Our recent study revealed that circulating mitochondria (C-Mito), a newly identified mediator of multi-organ communication, promote sympathoexcitation in HF by aggravating endothelial cell (EC)-derived neuroinflammation in the subfornical organ (SFO), the cardiovascular autonomic neural center. The precise molecular mechanism by which C-Mito promotes SFO-induced endothelial neuroinflammation has not been fully elucidated.

OBJECTIVE

C-Mito carrying cGAS promote sympathoexcitation by targeting PLA2G2A in ECs of the SFO in HF rats.

METHODS

Male Sprague-Dawley (SD) rats received a subcutaneous injection of isoprenaline (ISO) at a dosage of 5 mg/kg/day for seven consecutive days to establish a HF model. C-Mito were isolated from HF rats and evaluated. The level of cGAS, a dsDNA sensor recently discovered to be directly localized on the outer membrane of mitochondria, was detected in C-Mito. C-Mito from HF rats (C-MitoHF) or control rats (C-MitoCtrl) were intravenously infused into HF rats. The accumulation of C-Mito in the ECs in the SFO was detected via double immunofluorescence staining. The SFO was processed for RNA sequencing (RNA-Seq) analysis. Secreted group IIA phospholipase A2 (PLA2G2A), the key gene involved in C-MitoHF-associated SFO dysfunction, was identified via bioinformatics analysis. Upregulation of PLA2G2A in the SFO ECs was assessed via immunofluorescence staining and immunoblotting, and PLA2G2A activity was evaluated. The interaction between cGAS and PLA2G2A was detected via co-immunoprecipitation. The dowstream molecular mechanisms of which PLA2G2A induced astroglial/microglial activation were also investigated. AAV9-TIE-shRNA (PLA2G2A) was introduced into the SFO to specifically knockdown endothelial PLA2G2A. Neuronal activation and glial proinflammatory polarization in the SFO were also evaluated. Renal sympathetic nerve activity (RSNA) was measured to evaluate central sympathetic output. Cardiac sympathetic hyperinnervation, myocardial remodeling, and left ventricular systolic function were assessed in C-Mito-treated HF rats.

RESULTS

Respiratory functional incompetence and oxidative damage were observed in C-MitoHF compared with C-MitoCtrl. Surprisingly, cGAS protein levels in C-MitoHF were significantly higher than those in C-MitoCtrl, while blocking cGAS with its specific inhibitor, RU.521, mitigated respiratory dysfunction and oxidative injury in C-MitoHF. C-Mito entered the ECs of the SFO in HF rats. RNA sequencing revealed that PLA2G2A is a key molecule for the induction of SFO dysfunction by C-MitoHF. The immunoblotting and immunofluorescence results confirmed that, compared with C-MitoCtrl, C-MitoHF increased endothelial PLA2G2A expression in the SFO of HF rats, which could be alleviated by attenuating C-MitoHF-localized cGAS. Furthermore, we found that cGAS directly interacts with PLA2G2A, increased the activity of PLA2AG2, which produced arachidonic acid, and also promoted PLA2G2A secretion in brain ECs. In addition, the inhibition of PLA2G2A in brain ECs significantly mitigated the proinflammatory effect of conditioned cell culture medium from C-MitoHF-treated ECs on astroglia and microglia. Also, we found that PLA2G2A secreted from ECs insulted by C-Mito induced neuroinflammation through activating astriglial/microglial Integrin-alphavbeta3 in the SFO, which further promote central sympathetic overdrive in HF rats. Specific knockdown of endothelial PLA2G2A in the SFO mitigated C-MitoHF-induced presympathetic neuronal sensitization, cardiac sympathetic hyperinnervation, RSNA activation, myocardial remodeling, and systolic dysfunction in HF rats.

CONCLUSION

C-Mito carrying cGAS promoted cardiac sympathoexcitation by directly targeting PLA2G2A in the ECs of the SFO in HF rats. Secreted PLA2G2A derived from ECs insulted by C-Mito induced neuroinflammation through activating astriglial/microglial Integrin-alphavbeta3 in the SFO, which further promote central sympathetic overdrive in HF rats. Our study indicated that inhibiting cGAS in C-Mito might be a potential treatment for central sympathetic overdrive in HF.

SerpinB1 targeting safeguards against pathological cardiac hypertrophy and remodelling by suppressing cardiomyocyte pyroptosis and inflammation initiation

AIMS

While the pivotal role of inflammation in pathological cardiac hypertrophy and remodelling is widely acknowledged, the mechanisms triggering inflammation initiation remain largely obscure. This study aims to elucidate the role and mechanism of serpin family B member 1 (SerpinB1) in pro-inflammatory cardiomyocyte pyroptosis, heart inflammation, and cardiac remodelling.

METHODS AND RESULTS

C57BL/6J wild-type, inducible cardiac-specific SerpinB1 overexpression or knockout mice underwent transverse aortic constriction (TAC) surgery. Cardiac hypertrophy and remodelling were assessed through echocardiography and histology. Cardiomyocyte pyroptosis and heart inflammation were monitored. Adeno-associated virus 9 -mediated gene manipulations and molecular assays were employed to explore the mechanisms through which SerpinB1 regulates cardiomyocyte pyroptosis and heart inflammation. Finally, recombinant mouse SerpinB1 protein (rSerpinB1) was administrated both in vivo through osmotic minipump delivery and in vitro to investigate the therapeutic potential of SerpinB1 in cardiac remodelling. Myocardial SerpinB1 overexpression was up-regulated shortly upon TAC or phenylephrine challenge, with no further elevation during prolonged hypertrophic stimuli. It is important to note that cardiac-specific overexpression of SerpinB1 markedly attenuated TAC-induced cardiac remodelling, while deletion of SerpinB1 exacerbated it. At the mechanistic level, SerpinB1 gain-of-function inhibited cardiomyocyte pyroptosis and inflammation in hypertrophic hearts; the protective effect was nullified by overexpression of either cleaved N-terminal gasdermin D or cleaved caspase-1. Co-immunoprecipitation and confocal assays confirmed that SerpinB1 directly interacts with caspase-1 in cardiomyocytes. Remarkably, rSerpinB1 replicated the cardioprotective effect against cardiac hypertrophy and remodelling.

CONCLUSION

SerpinB1 safeguards against pathological cardiac hypertrophy and remodelling by impeding cardiomyocyte pyroptosis to suppress inflammation initiation, achieved through interaction with caspase-1 to inhibit its activation. Targeting SerpinB1 could represent a novel therapeutic strategy for treating pathological cardiac hypertrophy and remodelling.

Unveiling the molecular and cellular links between obstructive sleep apnea-hypopnea syndrome and vascular aging

ABSTRACT

Vascular aging (VA) is a common etiology of various chronic diseases and represents a major public health concern. Intermittent hypoxia (IH) associated with obstructive sleep apnea-hypopnea syndrome (OSAHS) is a primary pathological and physiological driver of OSAHS-induced systemic complications. A substantial proportion of OSAHS patients, estimated to be between 40% and 80%, have comorbidities such as hypertension, heart failure, coronary artery disease, pulmonary hypertension, atrial fibrillation, aneurysm, and stroke, all of which are closely associated with VA. This review examines the molecular and cellular features common to both OSAHS and VA, highlighting decreased melatonin secretion, impaired autophagy, increased apoptosis, increased inflammation and pyroptosis, increased oxidative stress, accelerated telomere shortening, accelerated stem cell depletion, metabolic disorders, imbalanced protein homeostasis, epigenetic alterations, and dysregulated neurohormonal signaling. The accumulation and combination of these features may underlie the pathophysiological link between OSAHS and VA, but the exact mechanisms by which OSAHS affects VA may require further investigation. Taken together, these findings suggest that OSAHS may serve as a novel risk factor for VA and related vascular disorders, and that targeting these features may offer therapeutic potential to mitigate the vascular risks associated with OSAHS.

Sirt1/Nrf2/TNFα; TLR4/Myd88/NF-κB signaling pathways are involved in mediating hepatoprotective effect of bupropion in rat model of myocardial infarction

BACKGROUND

The aim of the current study is to identify the possible protective effect of bupropion (BUP) on liver injury in rat model of myocardial infarction (MI). BUP was administered in the presence and absence of MI.

MATERIALS AND METHODS

Thirty-two Wistar adult male rats were randomly arranged into four groups: control, BUP (30 mg/kg/day, intraperitoneal) for 28 days, isoproterenol (ISO) was injected subcutaneous (85 mg/kg) in the 26th and 27th days and BUP/ISO groups. Cardiac and hepatic enzymes were measured, also Hepatic oxidative stress indicators, as well as inflammatory and apoptotic biomarkers, were evaluated. Cardiac and hepatic histopathological examination and hepatic nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) immunohistochemical study were also detected.

RESULTS

ISO significantly increased cardiac and hepatic enzymes, hepatic oxidative stress, inflammatory, apoptotic, with a histopathological picture of cardiac and hepatic damage and high hepatic NF-κB immunoexpression were detected. BUP significantly normalized the upraised oxidative, inflammatory, and apoptotic parameters, with an impressive improvement in the histopathological picture and a reduction in hepatic NF-κB immunoexpression.

CONCLUSION

BUP protects against liver injury on top of MI in rat model via modulation of Sirtuin type 1 (Sirt1)/Nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/tumor necrosis factor α (TNFα); Toll-like receptor 4 (TLR4)/Hepatic myeloid differentiation primary response 88(Myd88)/NF-κB signaling pathways.

Salbutamol attenuates arrhythmogenic effect of aminophylline in a hPSC-derived cardiac model

The combination of aminophylline and salbutamol is frequently used in clinical practice in the treatment of obstructive lung diseases. While the side effects (including arrhythmias) of the individual bronchodilator drugs were well described previously, the side effects of combined treatment are almost unknown. We aimed to study the arrhythmogenic potential of combined aminophylline and salbutamol treatment in vitro. For this purpose, we used the established atomic force microscopy (AFM) model coupled with cardiac organoids derived from human pluripotent stem cells (hPSC-CMs). We focused on the chronotropic, inotropic, and arrhythmogenic effects of salbutamol alone and aminophylline and salbutamol combined treatment. We used a method based on heart rate/beat rate variability (HRV/BRV) analysis to detect arrhythmic events in the hPSC-CM based AFM recordings. Salbutamol and aminophylline had a synergistic chronotropic and inotropic effect compared to the effects of monotherapy. Our main finding was that salbutamol reduced the arrhythmogenic effect of aminophylline, most likely mediated by endothelial nitric oxide synthase activated by beta-2 adrenergic receptors. These findings were replicated and confirmed using hPSC-CM derived from two cell lines (CCTL4 and CCTL12). Data suggest that salbutamol as an add-on therapy may not only deliver a bronchodilator effect but also increase the cardiovascular safety of aminophylline, as salbutamol reduces its arrhythmogenic potential.

USP20 deletion promotes eccentric cardiac remodeling in response to pressure overload and increases mortality

Left ventricular hypertrophy (LVH) caused by chronic pressure overload with subsequent pathological remodeling is a major cardiovascular risk factor for heart failure and mortality. The role of deubiquitinases in LVH has not been well characterized. To define whether the deubiquitinase ubiquitin-specific peptidase 20 (USP20) regulates LVH, we subjected USP20 knockout (KO) and cognate wild-type (WT) mice to chronic pressure overload by transverse aortic constriction (TAC) and measured changes in cardiac function by serial echocardiography followed by histological and biochemical evaluations. USP20-KO mice showed severe deterioration of systolic function within 4 wk of TAC compared with WT cohorts. Both USP20-KO TAC and WT-TAC cohorts presented cardiac hypertrophy following pressure overload. However, USP20-KO-TAC mice showed an increase in cardiomyocyte length and developed maladaptive eccentric hypertrophy, a phenotype generally observed with volume overload states and decompensated heart failure. In contrast, WT-TAC mice displayed an increase in cardiomyocyte width, producing concentric remodeling that is characteristic of pressure overload. In addition, cardiomyocyte apoptosis, interstitial fibrosis, and mouse mortality were augmented in USP20-KO-TAC compared with WT-TAC mice. Quantitative mass spectrometry of LV tissue revealed that the expression of sarcomeric myosin heavy chain 7 (MYH7), a fetal gene normally upregulated during cardiac remodeling, was significantly reduced in USP20-KO after TAC. Mechanistically, we identified increased degradative lysine-48 polyubiquitination of MYH7 in USP20-KO hearts, indicating that USP20-mediated deubiquitination likely prevents protein degradation of MYH7 during pressure overload. Our findings suggest that USP20-dependent signaling pathways regulate the layering pattern of sarcomeres to suppress maladaptive remodeling during chronic pressure overload and prevent cardiac failure.NEW & NOTEWORTHY We identify ubiquitin-specific peptidase 20 (USP20) as an important enzyme that is required for cardiac homeostasis and function, particularly during myocardial pressure overload. USP20 regulates protein stability of cardiac MYH7, an essential molecular motor protein expressed in sarcomeres; loss-of-function mutations of MYH7 are associated with human hypertrophic cardiomyopathy, cardiac failure, and sudden death. Enhancing USP20 activity could be a potential therapeutic approach to prevent the development of maladaptive state of eccentric hypertrophy and heart failure.

Regulation of β-Adrenergic Receptors in the Heart: A Review on Emerging Therapeutic Strategies for Heart Failure

The prolonged overstimulation of β-adrenergic receptors (β-ARs), a member of the G protein-coupled receptor (GPCR) family, causes abnormalities in the density and functionality of the receptor and contributes to cardiac dysfunctions, leading to the development and progression of heart diseases, especially heart failure (HF). Despite recent advancements in HF therapy, mortality and morbidity rates continue to be high. Treatment with β-AR antagonists (β-blockers) has improved clinical outcomes and reduced overall hospitalization and mortality rates. However, several barriers in the management of HF remain, providing opportunities to develop new strategies that focus on the functions and signal transduction of β-ARs involved in the pathogenesis of HF. As β-AR can signal through multiple pathways influenced by different receptor subtypes, expression levels, and signaling components such as G proteins, G protein-coupled receptor kinases (GRKs), β-arrestins, and downstream effectors, it presents a complex mechanism that could be targeted in HF management. In this narrative review, we focus on the regulation of β-ARs at the receptor, G protein, and effector loci, as well as their signal transductions in the physiology and pathophysiology of the heart. The discovery of potential ligands for β-AR that activate cardioprotective pathways while limiting off-target signaling is promising for the treatment of HF. However, applying findings from preclinical animal models to human patients faces several challenges, including species differences, the genetic variability of β-ARs, and the complexity and heterogeneity of humans. In this review, we also summarize recent updates and future research on the regulation of β-ARs in the molecular basis of HF and highlight potential therapeutic strategies for HF.

RelA-mediated signaling connects adaptation to chronic cardiomyocyte stress with myocardial and systemic inflammation in the ADCY8 model of accelerated aging

Mice with cardiac-specific overexpression of adenylyl cyclase (AC) type 8 (TGAC8) are under a constant state of severe myocardial stress. They have a remarkable ability to adapt to this stress, but they eventually develop accelerated cardiac aging and experience reduced longevity. We have previously demonstrated through bioinformatics that constitutive adenylyl cyclase activation in TGAC8 mice is associated with the activation of inflammation-related signaling pathways. However, the immune response associated with chronic myocardial stress in the TGAC8 mouse remains unexplored. Here we demonstrate that chronic activation of adenylyl cyclase in cardiomyocytes of TGAC8 mice results in activation of cell-autonomous RelA-mediated NF-κB signaling. This is associated with non-cell-autonomous activation of proinflammatory and age-associated signaling in myocardial endothelial cells and myocardial smooth muscle cells, expansion of myocardial immune cells, increase in serum levels of inflammatory cytokines, and changes in the size or composition of lymphoid organs. All these changes precede the appearance of cardiac fibrosis. We provide evidence indicating that RelA activation in cardiomyocytes with chronic activation of adenylyl cyclase is mediated by calcium-protein Kinase A (PKA) signaling. Using a model of chronic cardiomyocyte stress and accelerated aging, we highlight a novel, calcium/PKA/RelA-dependent connection between cardiomyocyte stress, myocardial inflammation, and systemic inflammation. These findings suggest that RelA-mediated signaling in cardiomyocytes might be an adaptive response to stress that, when chronically activated, ultimately contributes to both cardiac and systemic aging.

Long-term effects of siponimod on cardiovascular and autonomic nervous system in secondary progressive multiple sclerosis

Background

Siponimod, a second-generation, selective sphingosine 1-phosphate receptor (S1PR) 1 and 5 modulator, represents an important therapeutic choice for active secondary progressive multiple sclerosis (SPMS). Besides the beneficial immunomodulatory effects, siponimod impacts cardiovascular function through S1PR1 modulation. Short-term vagomimetic effects on cardiac activity have proved to be mitigated by dose titration. However, long-term consequences are less known.

Objectives

This study aimed to investigate the long-term impact of siponimod on cardiac autonomic modulation in people with SPMS (pwSPMS).

Methods

Heart rate variability (HRV) and vascular hemodynamic parameters were evaluated using Multiple Trigonometric Regressive Spectral analysis in 47 pwSPMS before siponimod therapy and after one, three, six and 12 months of treatment. Autonomic activation tests (tilt test for the sympathetic and deep breathing test for the parasympathetic cardiac modulation) were performed at each examination.

Results

pwSPMS preserved regular cardiovascular modulation responses during the autonomic tests reflected in the variation of several HRV parameters, such as RMSSD, pNN50, total power of HRV, high-frequency and low-frequency bands of the spectral domain or hemodynamic vascular parameters (Cwk, Zao, TPR, MAP) and baroreflex sensitivity (BRS). In the long-term follow-up, RMSSD, pNN50, total power, BRS and CwK presented a significant decrease, underlining a reduction of the parasympathetic and a shift towards sympathetic predominance in cardiac autonomic modulation that tends to stabilise after 1 year of treatment.

Conclusion

Due to dose titration, the short-term effects of siponimod on cardiac autonomic modulation are mitigated. The long-term impact on cardiac autonomic modulation is similar to fingolimod. The autonomic activation tests showed normal cardiovascular responses during 1-year follow-up in pwSPMS, confirming the safety profile of siponimod. Further research on autonomic function could reveal whether the observed sympathetic activation is a compensatory response to S1P signaling intervention or a feature of the disease, while also shedding light on the role of S1PR modulation in MS.

Developmental Changes in the Excitation-Contraction Mechanisms of the Ventricular Myocardium and Their Sympathetic Regulation in Small Experimental Animals

The developmental changes in the excitation-contraction mechanisms of the ventricular myocardium of small animals (guinea pig, rat, mouse) and their sympathetic regulation will be summarized. The action potential duration monotonically decreases during pre- and postnatal development in the rat and mouse, while in the guinea pig it decreases during the fetal stage but turns into an increase just before birth. Such changes can be attributed to changes in the repolarizing potassium currents. The T-tubule and the sarcoplasmic reticulum are scarcely present in the fetal cardiomyocyte, but increase during postnatal development. This causes a developmental shift in the Ca2+ handling from a sarcolemma-dependent mechanism to a sarcoplasmic reticulum-dependent mechanism. The sensitivity for beta-adrenoceptor-mediated positive inotropy decreases during early postnatal development, which parallels the increase in sympathetic nerve innervation. The alpha-adrenoceptor-mediated inotropy in the mouse changes from positive in the neonate to negative in the adult. This can be explained by the change in the excitation-contraction mechanism mentioned above. The shortening of the action potential duration enhances trans-sarcolemmal Ca2+ extrusion by the Na+-Ca2+ exchanger. The sarcoplasmic reticulum-dependent mechanism of contraction in the adult allows Na+-Ca2+ exchanger activity to cause negative inotropy, a mechanism not observed in neonatal myocardium. Such developmental studies would provide clues towards a more comprehensive understanding of cardiac function.

Combined non-targeted and targeted metabolomics reveals the mechanism of delaying aging of Ginseng fibrous root

Background: The fibrous root of ginseng (GFR) is the dried thin branch root or whisker root of Ginseng (Panax ginseng C. A. Mey). It is known for its properties such as tonifying qi, producing body fluid, and quenching thirst. Clinically, it is used to treat conditions such as cough, hemoptysis, thirst, stomach deficiency, and vomiting. While GFR and Ginseng share similar metabolites, they differ in their metabolites ratios and efficacy. Furthermore, the specific role of GFR in protecting the body remains unclear. Methods: We employed ultra-high performance liquid chromatography-triple quadrupole mass spectrometry to examine alterations in brain neurotransmitters and elucidate the impact of GFR on the central nervous system. Additionally, we analyzed the serum and brain metabolic profiles of rats using ultra-high performance liquid chromatography-quadrupole-orbitrap mass spectrometry to discern the effect and underlying mechanism of GFR in delaying aging in naturally aged rats. Results: The findings of the serum biochemical indicators indicate that the intervention of GFR can enhance cardiovascular, oxidative stress, and energy metabolism related indicators in naturally aging rats. Research on brain neurotransmitters suggests that GFR can augment physiological functions such as learning and memory, while also inhibiting central nervous system excitation to a certain degree by maintaining the equilibrium of central neurotransmitters in aged individuals. Twenty-four abnormal metabolites in serum and seventeen abnormal metabolites in brain could be used as potential biomarkers and were involved in multiple metabolic pathways. Among them, in the brain metabolic pathways, alanine, aspartate and glutamate metabolism, arginine and proline metabolism, histidine metabolism, and tyrosine metabolism were closely related to central neurotransmitters. Butanoate metabolism improves energy supply for life activities in the aging body. Cysteine and methionine metabolism contributes to the production of glutathione and taurine and played an antioxidant role. In serum, the regulation of glycerophospholipid metabolism pathway and proline metabolism demonstrated the antioxidant capacity of GFR decoction. Conclution: In summary, GFR plays a role in delaying aging by regulating central neurotransmitters, cardiovascular function, oxidative stress, energy metabolism, and other aspects of the aging body, which lays a foundation for the application of GFR.

Heart rate response to cognitive load as a marker of depression and increased anxiety

Introduction

Understanding the interplay between cardiovascular parameters, cognitive stress induced by increasing load, and mental well-being is vital for the development of integrated health strategies today. By monitoring physiological signals like electrocardiogram (ECG) and photoplethysmogram (PPG) in real time, researchers can discover how cognitive tasks influence both cardiovascular and mental health. Cardiac biomarkers resulting from cognitive strain act as indicators of autonomic nervous system function, potentially reflecting conditions related to heart and mental health, including depression and anxiety. The purpose of this study is to investigate how cognitive load affects ECG and PPG measurements and whether these can signal early cardiovascular changes during depression and anxiety disorders.

Methods

Ninety participants aged 18 to 45 years, ranging from symptom-free individuals to those with diverse psychological conditions, were assessed using psychological questionnaires and anamnesis. ECG and PPG monitoring were conducted as volunteers engaged in a cognitive 1-back task consisting of two separate blocks, each with six progressively challenging levels. The participants' responses were analyzed to correlate physiological and psychological data with cognitive stressors and outcomes.

Results

The study confirmed a notable interdependence between anxiety and depression, and cardiovascular responses. Task accuracy decreased with increased task difficulty. A strong relationship between PPG-measured heart rate and markers of depression and trait anxiety was observed. Increasing task difficulty corresponded to an increase in heart rate, linked with elevated levels of depression and trait anxiety. A strong relationship between ECG-measured heart rate and anxiety attacks was observed. Increasing task difficulty corresponded to an increase in heart rate, linked with elevated levels of anxiety attacks, although this association decreased under more challenging conditions.

Discussion

The findings underscore the predictive importance of ECG and PPG heart rate parameters in mental health assessment, particularly depression and anxiety under cognitive stress induced by increasing load. We discuss mechanisms of sympathetic activation explaining these differences. Our research outcomes have implications for clinical assessments and wearable device algorithms for more precise, personalized mental health diagnostics.

Genetic Variants of the Beta-Adrenergic Receptor Pathways as Both Risk and Protective Factors for Retinopathy of Prematurity

PURPOSE

There is strong evidence that genetic factors influence retinopathy of prematurity (ROP), a neovascular eye disease. It has been previously suggested that polymorphisms in the genes involved in β-adrenergic receptor (ADRβ) pathways could protect against ROP. Antagonists for the ADRβ are actively tested in clinical trials for ROP treatment, but not without controversy and safety concerns. This study was designed to assess whether genetic variations in components of the ADRβ signaling pathways associate with risk of developing ROP.

DESIGN

An observational case-control targeted genetic analysis.

METHODS

A study was carried out in premature participants with (n = 30) or without (n = 34) ROP and full-term controls (n = 20), who were divided into a discovery cohort and a validation cohort. ROP was defined using International Classification of Retinopathy of Prematurity criteria (ICROP). Targeted sequencing of 20 genes in the ADRβ pathways was performed in the discovery cohort. Polymerase chain reaction (PCR)/restriction enzyme analysis for some of the discovered ROP-associated variants was performed for validation of the results using the validation cohort.

RESULTS

The discovery cohort revealed 543 bi-allelic variants within 20 genes of the ADRβ pathways. Ten single-nucleotide variants (SNVs) in 5 genes including protein kinase A regulatory subunit 1α (PRKAR1A), rap guanine exchange factor 3 (RAPGEF3), adenylyl cyclase 4 (ADCY4), ADCY7, and ADCY9 were associated with ROP (P < .05). The most significant SNV was found in PRKAR1A (P = .001). Multiple variants located in the 3'-untranslated region (3'UTR) of RAPGEF3 were also associated with ROP (P < .05). PCR/restriction enzyme analysis of the 3'UTR of RAPGEF3 methodologically validated these findings.

CONCLUSION

SNVs in PRKAR1A may represent protective factors whereas SNVs in RAPGEF3 may represent risk factors for ROP. PRKAR1α has previously been implicated in retinal vascular development whereas the RAPGEF3 product has a role in the maintenance of vascular barrier function, 2 processes important in ROP. Multicenter validation of these newly discovered risk factors could lead to valuable tools for predicting and preventing the development of severe ROP.

Targeting G protein-coupled receptors for heart failure treatment

Heart failure remains a leading cause of morbidity and mortality worldwide. Current treatment for patients with heart failure include drugs targeting G protein-coupled receptors such as β-adrenoceptor antagonists (β-blockers) and angiotensin II type 1 receptor antagonists (or angiotensin II receptor blockers). However, many patients progress to advanced heart failure with persistent symptoms, despite treatment with available therapeutics that have been shown to reduce mortality and mortality. GPCR targets currently being explored for the development of novel heart failure therapeutics include adenosine receptor, formyl peptide receptor, relaxin/insulin-like family peptide receptor, vasopressin receptor, endothelin receptor and the glucagon-like peptide 1 receptor. Many GPCR drug candidates are limited by insufficient efficacy and/or dose-limiting unwanted effects. Understanding the current challenges hindering successful clinical translation and the potential to overcome existing limitations will facilitate the future development of novel heart failure therapeutics. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Optical control of cell-surface and endomembrane-exclusive β-adrenergic receptor signaling

Beta-adrenergic receptors (βARs) are G protein-coupled receptors (GPCRs) that mediate catecholamine hormone-induced stress responses, such as elevation of heart rate. Besides those that are plasma membrane-bound, endomembrane βARs are also signaling competent. Dysregulation of βAR pathways underlies severe pathological conditions. Emerging evidence indicates pathological molecular signatures in deeper endomembrane βARs signaling, likely contributing to conditions such as cardiomyocyte hypertrophy and apoptosis. However, the lack of approaches to control endomembrane β1ARs has impeded linking signaling with pathology. Informed by the β1AR-catecholamine interactions, we engineered an efficient photolabile proligand (OptoIso) to trigger βAR signaling exclusively in endomembrane regions using blue light stimulation. Not only does OptoIso undergo blue light deprotection in seconds, but also efficiently enters cells and allows examination of G protein heterotrimer activation exclusively at endomembranes. OptoIso also allows optical activation of plasma membrane βAR signaling in selected single cells with native fidelity, which can be reversed by terminating blue light. Thus, OptoIso will be a valuable experimental tool to elicit spatial and temporal control of βAR signaling in user-defined endomembrane or plasma membrane regions in unmodified cells with native fidelity.

Metabolomics analysis reveals the effects of Salvia Miltiorrhiza Bunge extract on ameliorating acute myocardial ischemia in rats induced by isoproterenol

Salvia miltiorrhiza Bunge (SM) is a widespread herbal therapy for myocardial ischemia (MI). Nevertheless, the therapeutic signaling networks of SM extract on MI is yet unknown. Emerging evidences suggested that alterations in cardiac metabolite influences host metabolism and accelerates MI progression. Herein, we employed an isoproterenol (ISO)-induced acute myocardial ischemia (AMI) rat model to confirm the pharmacological effects of SM extract (0.8, 0.9, 1.8 g/kg/day) via assessment of the histopathological alterations that occur within the heart tissue and associated cytokines; we also examined the underlying SM extract-mediated signaling networks using untargeted metabolomics. The results indicated that 25 compounds with a relative content higher than 1 % in SM aqueous extract were identified using LC-MS/MS analysis, which included salvianolic acid B, lithospermic acid, salvianolic acid A, and caffeic acid as main components. An in vivo experiment showed that pretreatment with SM extract attenuated ISO-induced myocardial injury, shown as decreased myocardial ischemic size, transformed electrocardiographic, histopathological, and serum biochemical aberrations, reduced levels of proinflammatory cytokines, inhibited oxidative stress (OS), and reversed the trepidations of the cardiac tissue metabolic profiles. Metabolomics analysis shows that the levels of 24 differential metabolites (DMs) approached the same value as controls after SM extract therapy, which were primarily involved in histidine; alanine, aspartate, and glutamate; glycerophospholipid; and glycine, serine, and threonine metabolisms through metabolic pathway analysis. Correlation analysis demonstrated that the levels of modulatory effects of SM extract on the inflammation and OS were related to alterations in endogenous metabolites. Overall, SM extract demonstrated significant cardioprotective effects in an ISO-induced AMI rat model, alleviating myocardial injury, inflammation and oxidative stress, with metabolomics analysis indicating potential therapeutic pathways for myocardial ischemia.

Adrenoceptor Desensitization: Current Understanding of Mechanisms

G-protein coupled receptors (GPCRs) transduce a wide range of extracellular signals. They are key players in the majority of biologic functions including vision, olfaction, chemotaxis, and immunity. However, as essential as most of them are to body function and homeostasis, overactivation of GPCRs has been implicated in many pathologic diseases such as cancer, asthma, and heart failure (HF). Therefore, an important feature of G protein signaling systems is the ability to control GPCR responsiveness, and one key process to control overstimulation involves initiating receptor desensitization. A number of steps are appreciated in the desensitization process, including cell surface receptor phosphorylation, internalization, and downregulation. Rapid or short-term desensitization occurs within minutes and involves receptor phosphorylation via the action of intracellular protein kinases, the binding of β-arrestins, and the consequent uncoupling of GPCRs from their cognate heterotrimeric G proteins. On the other hand, long-term desensitization occurs over hours to days and involves receptor downregulation or a decrease in cell surface receptor protein level. Of the proteins involved in this biologic phenomenon, β-arrestins play a particularly significant role in both short- and long-term desensitization mechanisms. In addition, β-arrestins are involved in the phenomenon of biased agonism, where the biased ligand preferentially activates one of several downstream signaling pathways, leading to altered cellular responses. In this context, this review discusses the different patterns of desensitization of the α 1-, α 2- and the β adrenoceptors and highlights the role of β-arrestins in regulating physiologic responsiveness through desensitization and biased agonism. SIGNIFICANCE STATEMENT: A sophisticated network of proteins orchestrates the molecular regulation of GPCR activity. Adrenoceptors are GPCRs that play vast roles in many physiological processes. Without tightly controlled desensitization of these receptors, homeostatic imbalance may ensue, thus precipitating various diseases. Here, we critically appraise the mechanisms implicated in adrenoceptor desensitization. A better understanding of these mechanisms helps identify new druggable targets within the GPCR desensitization machinery and opens exciting therapeutic fronts in the treatment of several pathologies.

Age- and sex-specific 99th percentile upper reference limits for high-sensitivity cardiac troponin T in Chinese older people: Real-world data mining

BACKGROUND

This study aims to investigate the impact of age and sex on high-sensitivity cardiac troponin T (hs-cTnT) and establish 99th percentile upper reference limits (URLs) in older individuals utilizing large-scale real-world data.

METHODS

40,530 outpatient hs-cTnT results were obtained from the laboratory database from January 1, 2018, to December 31, 2023. Our study included 4,199 elderly outpatients (aged ≥ 60) without cardiovascular disease or other heart-related chronic conditions. Nested analysis of variance was used to explore the necessity of partitioning reference intervals (RIs) by sex and age groups. RIs were established by the refineR algorithm and assessed based on ≤ 10% test results of validation data set outside the new RIs.

RESULTS

RIs for hs-cTnT in the older population needed to be partitioned by sex and age groups ([standard deviation ratio] SDRage = 0.75; SDRsex = 0.49). URLs in older Chinese adults were 21.8 ng/L for males, 16.5 ng/L for females, and 20.7 ng/L for the overall participant group. URLs for males aged 60-69, 70-79, and ≥ 80 were 13.7, 19.4, and 31.0 ng/L, respectively. Female values were 10.1, 17.2, and 22.0 ng/L. Importantly, manufacturer-reported RIs do not suffice for Chinese individuals aged ≥ 70. Validation data showed that 2.7-5.2% of test results fell outside the new RIs, confirming the validity of the results.

CONCLUSION

This study establishes age- and sex-specific 99th percentile URLs for hs-cTnT in Chinese older individuals, thereby enhancing the accuracy of clinical assessments.

Calorie restriction anti-hypertrophic effects are associated with improved mitochondrial content, blockage of Ca2+-induced mitochondrial damage, and lower reverse electron transport-mediated oxidative stress

Calorie restriction is a nutritional intervention that reproducibly protects against the maladaptive consequences of cardiovascular diseases. Pathological cardiac hypertrophy leads to cellular growth, dysfunction (with mitochondrial dysregulation), and oxidative stress. The mechanisms behind the cardiovascular protective effects of calorie restriction are still under investigation. In this study, we show that this dietetic intervention prevents cardiac protein elevation, avoids fetal gene reprogramming (atrial natriuretic peptide), and blocks the increase in heart weight per tibia length index (HW/TL) seen in isoproterenol-induced cardiac hypertrophy. Our findings suggest that calorie restriction inhibits cardiac pathological growth while also lowering mitochondrial reverse electron transport-induced hydrogen peroxide formation and improving mitochondrial content. Calorie restriction also attenuated the opening of the Ca2+-induced mitochondrial permeability transition pore. We also found that calorie restriction blocked the negative correlation of antioxidant enzymes (superoxide dimutase and glutatione peroxidase activity) and HW/TL, leading to the maintenance of protein sulphydryls and glutathione levels. Given the nature of isoproterenol-induced cardiac hypertrophy, we investigated whether calorie restriction could alter cardiac beta-adrenergic sensitivity. Using isolated rat hearts in a Langendorff system, we found that calorie restricted hearts have preserved beta-adrenergic signaling. In contrast, hypertrophic hearts (treated for seven days with isoproterenol) were insensitive to beta-adrenergic activation using isoproterenol (50 nM). Despite protecting against cardiac hypertrophy, calorie restriction did not alter the lack of responsiveness to isoproterenol in isolated hearts harvested from isoproterenol-treated rats. These results suggest (through a series of mitochondrial, oxidative stress, and cardiac hemodynamic studies) that calorie restriction possesses beneficial effects against hypertrophic cardiomyopathy.

Optical Control of Cell-Surface and Endomembrane-Exclusive β-Adrenergic Receptor Signaling

Beta-adrenergic receptors (βARs) are G protein-coupled receptors (GPCRs) that mediate catecholamine-induced stress responses, such as heart rate increase and bronchodilation. In addition to signals from the cell surface, βARs also broadcast non-canonical signaling activities from the cell interior membranes (endomembranes). Dysregulation of these receptor pathways underlies severe pathological conditions. Excessive βAR stimulation is linked to cardiac hypertrophy, leading to heart failure, while impaired stimulation causes compromised fight or flight stress responses and homeostasis. In addition to plasma membrane βAR, emerging evidence indicates potential pathological implications of deeper endomembrane βARs, such as inducing cardiomyocyte hypertrophy and apoptosis, underlying heart failure. However, the lack of approaches to control their signaling in subcellular compartments exclusively has impeded linking endomembrane βAR signaling with pathology. Informed by the β1AR-catecholamine interactions, we engineered an efficiently photo-labile, protected hydroxy β1AR pro-ligand (OptoIso) to trigger βAR signaling at the cell surface, as well as exclusive endomembrane regions upon blue light stimulation. Not only does OptoIso undergo blue light deprotection in seconds, but it also efficiently enters cells and allows examination of G protein heterotrimer activation exclusively at endomembranes. In addition to its application in the optical interrogation of βARs in unmodified cells, given its ability to control deep organelle βAR signaling, OptoIso will be a valuable experimental tool.

Protein-protein interaction network-based integration of GWAS and functional data for blood pressure regulation analysis

BACKGROUND

It is valuable to analyze the genome-wide association studies (GWAS) data for a complex disease phenotype in the context of the protein-protein interaction (PPI) network, as the related pathophysiology results from the function of interacting polyprotein pathways. The analysis may include the design and curation of a phenotype-specific GWAS meta-database incorporating genotypic and eQTL data linking to PPI and other biological datasets, and the development of systematic workflows for PPI network-based data integration toward protein and pathway prioritization. Here, we pursued this analysis for blood pressure (BP) regulation.

METHODS

The relational scheme of the implemented in Microsoft SQL Server BP-GWAS meta-database enabled the combined storage of: GWAS data and attributes mined from GWAS Catalog and the literature, Ensembl-defined SNP-transcript associations, and GTEx eQTL data. The BP-protein interactome was reconstructed from the PICKLE PPI meta-database, extending the GWAS-deduced network with the shortest paths connecting all GWAS-proteins into one component. The shortest-path intermediates were considered as BP-related. For protein prioritization, we combined a new integrated GWAS-based scoring scheme with two network-based criteria: one considering the protein role in the reconstructed by shortest-path (RbSP) interactome and one novel promoting the common neighbors of GWAS-prioritized proteins. Prioritized proteins were ranked by the number of satisfied criteria.

RESULTS

The meta-database includes 6687 variants linked with 1167 BP-associated protein-coding genes. The GWAS-deduced PPI network includes 1065 proteins, with 672 forming a connected component. The RbSP interactome contains 1443 additional, network-deduced proteins and indicated that essentially all BP-GWAS proteins are at most second neighbors. The prioritized BP-protein set was derived from the union of the most BP-significant by any of the GWAS-based or the network-based criteria. It included 335 proteins, with ~ 2/3 deduced from the BP PPI network extension and 126 prioritized by at least two criteria. ESR1 was the only protein satisfying all three criteria, followed in the top-10 by INSR, PTN11, CDK6, CSK, NOS3, SH2B3, ATP2B1, FES and FINC, satisfying two. Pathway analysis of the RbSP interactome revealed numerous bioprocesses, which are indeed functionally supported as BP-associated, extending our understanding about BP regulation.

CONCLUSIONS

The implemented workflow could be used for other multifactorial diseases.

Persistent PKA activation redistributes NaV1.5 to the cell surface of adult rat ventricular myocytes

During chronic stress, persistent activation of cAMP-dependent protein kinase (PKA) occurs, which can contribute to protective or maladaptive changes in the heart. We sought to understand the effect of persistent PKA activation on NaV1.5 channel distribution and function in cardiomyocytes using adult rat ventricular myocytes as the main model. PKA activation with 8CPT-cAMP and okadaic acid (phosphatase inhibitor) caused an increase in Na+ current amplitude without altering the total NaV1.5 protein level, suggesting a redistribution of NaV1.5 to the myocytes' surface. Biotinylation experiments in HEK293 cells showed that inhibiting protein trafficking from intracellular compartments to the plasma membrane prevented the PKA-induced increase in cell surface NaV1.5. Additionally, PKA activation induced a time-dependent increase in microtubule plus-end binding protein 1 (EB1) and clustering of EB1 at myocytes' peripheral surface and intercalated discs (ICDs). This was accompanied by a decrease in stable interfibrillar microtubules but an increase in dynamic microtubules along the myocyte surface. Imaging and coimmunoprecipitation experiments revealed that NaV1.5 interacted with EB1 and β-tubulin, and both interactions were enhanced by PKA activation. We propose that persistent PKA activation promotes NaV1.5 trafficking to the peripheral surface of myocytes and ICDs by providing dynamic microtubule tracks and enhanced guidance by EB1. Our proposal is consistent with an increase in the correlative distribution of NaV1.5, EB1, and β-tubulin at these subcellular domains in PKA-activated myocytes. Our study suggests that persistent PKA activation, at least during the initial phase, can protect impulse propagation in a chronically stressed heart by increasing NaV1.5 at ICDs.

Inside the Biology of the β3-Adrenoceptor

Since the first discovery in 1989, the β3-adrenoceptor (β3-AR) has gained great attention because it showed the ability to regulate many physiologic and metabolic activities, such as thermogenesis and lipolysis in brown and white adipose tissue, respectively (BAT, WAT), negative inotropic effects in cardiomyocytes, and relaxation of the blood vessels and the urinary bladder. The β3-AR has been suggested as a potential target for cancer treatment, both in adult and pediatric tumors, since under hypoxia its upregulation in the tumor microenvironment (TME) regulates stromal cell differentiation, tumor growth and metastases, signifying that its agonism/antagonism could be useful for clinical benefits. Promising results in cancer research have proposed the β3-AR being targeted for the treatment of many conditions, with some drugs, at present, undergoing phase II and III clinical trials. In this review, we report the scientific journey followed by the research from the β3-Ars' discovery, with focus on the β3-Ars' role in cancer initiation and progression that elects it an intriguing target for novel antineoplastic approaches. The overview highlights the great potential of the β3-AR, both in physiologic and pathologic conditions, with the intention to display the possible benefits of β3-AR modulation in cancer reality.

Circulating mitochondria promoted endothelial cGAS-derived neuroinflammation in subfornical organ to aggravate sympathetic overdrive in heart failure mice

BACKGROUND

Sympathoexcitation contributes to myocardial remodeling in heart failure (HF). Increased circulating pro-inflammatory mediators directly act on the Subfornical organ (SFO), the cardiovascular autonomic center, to increase sympathetic outflow. Circulating mitochondria (C-Mito) are the novel discovered mediators for inter-organ communication. Cyclic GMP-AMP synthase (cGAS) is the pro-inflammatory sensor of damaged mitochondria.

OBJECTIVES

This study aimed to assess the sympathoexcitation effect of C-Mito in HF mice via promoting endothelial cGAS-derived neuroinflammation in the SFO.

METHODS

C-Mito were isolated from HF mice established by isoprenaline (0.0125 mg/kg) infusion via osmotic mini-pumps for 2 weeks. Structural and functional analyses of C-Mito were conducted. Pre-stained C-Mito were intravenously injected every day for 2 weeks. Specific cGAS knockdown (cGAS KD) in the SFO endothelial cells (ECs) was achieved via the administration of AAV9-TIE-shRNA (cGAS) into the SFO. The activation of cGAS in the SFO ECs was assessed. The expression of the mitochondrial redox regulator Dihydroorotate dehydrogenase (DHODH) and its interaction with cGAS were also explored. Neuroinflammation and neuronal activation in the SFO were evaluated. Sympathetic activity, myocardial remodeling, and cardiac systolic dysfunction were measured.

RESULTS

C-Mito were successfully isolated, which showed typical structural characteristics of mitochondria with double-membrane and inner crista. Further analysis showed impaired respiratory complexes activities of C-Mito from HF mice (C-MitoHF) accompanied by oxidative damage. C-Mito entered ECs, instead of glial cells and neurons in the SFO of HF mice. C-MitoHF increased the level of ROS and cytosolic free double-strand DNA (dsDNA), and activated cGAS in cultured brain endothelial cells. Furthermore, C-MitoHF highly expressed DHODH, which interacted with cGAS to facilitate endothelial cGAS activation. C-MitoHF aggravated endothelial inflammation, microglial/astroglial activation, and neuronal sensitization in the SFO of HF mice, which could be ameliorated by cGAS KD in the ECs of the SFO. Further analysis showed C-MitoHF failed to exacerbate sympathoexcitation and myocardial sympathetic hyperinnervation in cGAS KD HF mice. C-MitoHF promoted myocardial fibrosis and hypertrophy, and cardiac systolic dysfunction in HF mice, which could be ameliorated by cGAS KD.

CONCLUSION

Collectively, we demonstrated that damaged C-MitoHF highly expressed DHODH, which promoted endothelial cGAS activation in the SFO, hence aggravating the sympathoexcitation and myocardial injury in HF mice, suggesting that C-Mito might be the novel therapeutic target for sympathoexcitation in HF.

CardiOmics signatures reveal therapeutically actionable targets and drugs for cardiovascular diseases

Cardiovascular diseases are the leading cause of death worldwide, with heart failure being a complex condition that affects millions of individuals. Single-nucleus RNA sequencing has recently emerged as a powerful tool for unraveling the molecular mechanisms behind cardiovascular diseases. This cutting-edge technology enables the identification of molecular signatures, intracellular networks, and spatial relationships among cardiac cells, including cardiomyocytes, mast cells, lymphocytes, macrophages, lymphatic endothelial cells, endocardial cells, endothelial cells, epicardial cells, adipocytes, fibroblasts, neuronal cells, pericytes, and vascular smooth muscle cells. Despite these advancements, the discovery of essential therapeutic targets and drugs for precision cardiology remains a challenge. To bridge this gap, we conducted comprehensive in silico analyses of single-nucleus RNA sequencing data, functional enrichment, protein interactome network, and identification of the shortest pathways to physiological phenotypes. This integrated multi-omics analysis generated CardiOmics signatures, which allowed us to pinpoint three therapeutically actionable targets (ADRA1A1, PPARG, and ROCK2) and 15 effective drugs, including adrenergic receptor agonists, adrenergic receptor antagonists, norepinephrine precursors, PPAR receptor agonists, and Rho-associated kinase inhibitors, involved in late-stage cardiovascular disease clinical trials.

Development of a new class of potent and highly selective G protein-coupled receptor kinase 5 inhibitors and structural insight from crystal structures of inhibitor complexes

G protein-coupled receptor kinase 5 (GRK5) is an important drug development target for heart failure, cardiac hypertrophy, and cancer. We have designed and developed a new class of highly selective, potent, and non-covalent GRK5 inhibitors. One of the inhibitors displayed GRK5 IC50 value of 10 nM and exhibited >100,000-fold selectivity over GRK2. The X-ray structure of a ketoamide-derived inhibitor-bound GRK5 showed the formation of a hemithioketal intermediate with active site Cys474 in the GRK5 active site and provided new insights into the ligand-binding site interactions responsible for high selectivity. The current studies serve as an important guide to therapeutic GRK5 inhibitor drug development.

PDE4D mediates impaired β-adrenergic receptor signalling in the sinoatrial node in mice with hypertensive heart disease

AIMS

The sympathetic nervous system increases HR by activating β-adrenergic receptors (β-ARs) and increasing cAMP in sinoatrial node (SAN) myocytes while phosphodiesterases (PDEs) degrade cAMP. Chronotropic incompetence, the inability to regulate heart rate (HR) in response to sympathetic nervous system activation, is common in hypertensive heart disease; however, the basis for this is poorly understood. The objective of this study was to determine the mechanisms leading to chronotropic incompetence in mice with angiotensin II (AngII)-induced hypertensive heart disease.

METHODS AND RESULTS

C57BL/6 mice were infused with saline or AngII (2.5 mg/kg/day for 3 weeks) to induce hypertensive heart disease. HR and SAN function in response to the β-AR agonist isoproterenol (ISO) were studied in vivo using telemetry and electrocardiography, in isolated atrial preparations using optical mapping, in isolated SAN myocytes using patch-clamping, and using molecular biology. AngII-infused mice had smaller increases in HR in response to physical activity and during acute ISO injection. Optical mapping of the SAN in AngII-infused mice demonstrated impaired increases in conduction velocity and altered conduction patterns in response to ISO. Spontaneous AP firing responses to ISO in isolated SAN myocytes from AngII-infused mice were impaired due to smaller increases in diastolic depolarization (DD) slope, hyperpolarization-activated current (If), and L-type Ca2+ current (ICa,L). These changes were due to increased localization of PDE4D surrounding β1- and β2-ARs in the SAN, increased SAN PDE4 activity, and reduced cAMP generation in response to ISO. Knockdown of PDE4D using a virus-delivered shRNA or inhibition of PDE4 with rolipram normalized SAN sensitivity to β-AR stimulation in AngII-infused mice.

CONCLUSIONS

AngII-induced hypertensive heart disease results in impaired HR responses to β-AR stimulation due to up-regulation of PDE4D and reduced effects of cAMP on spontaneous AP firing in SAN myocytes.

Exploring the Regulation and Function of Rpl3l in the Development of Early-Onset Dilated Cardiomyopathy and Congestive Heart Failure Using Systems Genetics Approach

BACKGROUND

Cardiomyopathies, diseases affecting the myocardium, are common causes of congestive heart failure (CHF) and sudden cardiac death. Recently, biallelic variants in ribosomal protein L3-like (RPL3L) have been reported to be associated with severe neonatal dilated cardiomyopathy (DCM) and CHF. This study employs a systems genetics approach to gain understanding of the regulatory mechanisms underlying the role of RPL3L in DCM.

METHODS

Genetic correlation, expression quantitative trait loci (eQTL) mapping, differential expression analysis and comparative functional analysis were performed using cardiac gene expression data from the patients and murine genetic reference populations (GRPs) of BXD mice (recombinant inbred strains from a cross of C57BL/6J and DBA/2J mice). Additionally, immune infiltration analysis was performed to understand the relationship between DCM, immune cells and RPL3L expression.

RESULTS

Systems genetics analysis identified high expression of Rpl3l mRNA, which ranged from 11.31 to 12.16 across murine GRPs of BXD mice, with an ~1.8-fold difference. Pathways such as "diabetic cardiomyopathy", "focal adhesion", "oxidative phosphorylation" and "DCM" were significantly associated with Rpl3l. eQTL mapping suggested Myl4 (Chr 11) and Sdha (Chr 13) as the upstream regulators of Rpl3l. The mRNA expression of Rpl3l, Myl4 and Sdha was significantly correlated with multiple echocardiography traits in BXD mice. Immune infiltration analysis revealed a significant association of RPL3L and SDHA with seven immune cells (CD4, CD8-naive T cell, CD8 T cell, macrophages, cytotoxic T cell, gamma delta T cell and exhausted T cell) that were also differentially infiltrated between heart samples obtained from DCM patients and normal individuals.

CONCLUSIONS

RPL3L is highly expressed in the heart tissue of humans and mice. Expression of Rpl3l and its upstream regulators, Myl4 and Sdha, correlate with multiple cardiac function traits in murine GRPs of BXD mice, while RPL3L and SDHA correlate with immune cell infiltration in DCM patient hearts, suggesting important roles for RPL3L in DCM and CHF pathogenesis via immune inflammation, necessitating experimental validations of Myl4 and Sdha in Rpl3l regulation.

Role of the autonomic nervous system in young, middle-aged, and older individuals with essential hypertension and sleep-related changes in neurocardiac regulation

Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep-wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep-wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30-79 years. They were stratified by age into young (< 40 years), middle-aged (40-59 years), and older (60-79 years) groups. Polysomnography and blood pressure data were recorded for 2 min before and during an hour-long nap. Autonomic function was assessed by measuring heart rate variability and blood pressure variability. Data were analyzed using t tests, correlation analyses, and two-way analysis of variance. During nonrapid eye movement (nREM), a main effect of age was observed on cardiac parasympathetic measures and baroreflex sensitivity (BRS), with the highest and lowest levels noted in the younger and older groups, respectively. The coefficients of the correlations between these measures and age were lower in patients with hypertension than in normotensive controls. The BRS of young patients with hypertension was similar to that of their middle-aged and older counterparts. However, cardiac sympathetic activity was significantly higher (p = 0.023) and BRS was significantly lower (p = 0.022) in the hypertension group than in the control group. During wakefulness, the results were similar although some of the above findings were absent. Autonomic imbalance, particularly impaired baroreflex, plays a more significant role in younger patients with hypertension. The nREM stage may be suitable for gaining insights into the relevant mechanisms.

β-adrenergic receptor regulates embryonic epithelial extensibility through actomyosin inhibition

During morphogenesis, epithelial tissues reshape and expand to cover the body and organs. The molecular mechanisms of this deformability remain elusive. Here, we investigate the role of the β-adrenergic receptor (ADRB) in orchestrating actomyosin contractility, pivotal for epithelial extensibility. Chemical screens on Xenopus laevis embryos pinpointed ADRB2 as a principal regulator. ADRB2 promotes actomyosin relaxation, facilitating apical cell area expansion during body elongation. In contrast, ADRB2 knockdown results in heightened cell contraction, marked by synchronous oscillation of F-actin and myosin, impeding body elongation. ADRB2 mutants with reduced affinity for ligand binding lack the function to induce cellular relaxation, highlighting the ligand's essential roles even in the developing epidermis. Our findings unveil ADRB2's critical contribution to extensibility of the epidermis and subsequent body elongation during development. This study also offers insights into the physiology of mature epithelial organs deformed by the smooth muscle response to the adrenergic autonomic nervous system.

What matters in aging is signaling for responsiveness

Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.

Cardiac optogenetics: shining light on signaling pathways

In the early 2000s, the field of neuroscience experienced a groundbreaking transformation with the advent of optogenetics. This innovative technique harnesses the properties of naturally occurring and genetically engineered rhodopsins to confer light sensitivity upon target cells. The remarkable spatiotemporal precision offered by optogenetics has provided researchers with unprecedented opportunities to dissect cellular physiology, leading to an entirely new level of investigation. Initially revolutionizing neuroscience, optogenetics quickly piqued the interest of the wider scientific community, and optogenetic applications were expanded to cardiovascular research. Over the past decade, researchers have employed various optical tools to observe, regulate, and steer the membrane potential of excitable cells in the heart. Despite these advancements, achieving control over specific signaling pathways within the heart has remained an elusive goal. Here, we review the optogenetic tools suitable to control cardiac signaling pathways with a focus on GPCR signaling, and delineate potential applications for studying these pathways, both in healthy and diseased hearts. By shedding light on these exciting developments, we hope to contribute to the ongoing progress in basic cardiac research to facilitate the discovery of novel therapeutic possibilities for treating cardiovascular pathologies.

Associations between Selected ADRB1 and CYP2D6 Gene Polymorphisms in Children with Ventricular and Supraventricular Arrhythmias

Background and Objectives: Tachycardia is a common cardiovascular disease. Drugs blocking β1-adrenergic receptors (ADRB1) are used in the therapy of arrhythmogenic heart diseases. Disease-related polymorphisms can be observed within the ADRB1 gene. The two most important are Ser49Gly and Arg389Gly, and they influence the treatment efficacy. The family of the cytochrome P450 system consists of the isoenzyme CYP2D6 (Debrisoquine 4-hydroxylase), which is involved in phase I metabolism of almost 25% of clinically important drugs, including antiarrhythmic drugs. A study was conducted to detect the ADRB1 and CYP2D6 gene polymorphisms. Materials and Methods: The material for the test was whole blood from 30 patients with ventricular and supraventricular tachycardia and 20 controls. The samples were obtained from the Department of Pediatric Cardiology. The first to be made was the extraction of DNA using a GeneMATRIX Quick Blood DNA Purification Kit from EURx. The selected ADRB1 and CYP2D6 gene polymorphisms were detected by high-resolution melting polymerase chain reaction (HRM-PCR) analysis. Results: Based on the analysis of melt profile data for each PCR product, the identification of polymorphisms was carried out. Heterozygotes and homozygotes were found in the examined alleles. Conclusions: The frequency of the Arg389Gly polymorphism differs statistically significantly between the control group and patients with supraventricular and ventricular arrhythmias, as well as between these two groups of patients. Moreover, the Arg389Gly polymorphism was statistically more prevalent in the group of girls with SVT arrhythmia compared to girls with VT. A few carriers of homozygous and heterozygous systems of the S49G polymorphism were detected among patients with arrhythmias, as well as control group. The percentage of individuals carrying the CYP2D6 4 allele as either homozygous or heterozygous was observed in the study and control groups. The high prevalence of the CYP2D6*4 allele carriers in both groups prompts the optimization of beta-1 blocker therapy.

SGLT2 Inhibitors in Aging-Related Cardiovascular Disease: A Review of Potential Mechanisms

Population aging combined with higher susceptibility to cardiovascular diseases in older adults is increasing the incidence of conditions such as atherosclerosis, myocardial infarction, heart failure, myocardial hypertrophy, myocardial fibrosis, arrhythmia, and hypertension. sodium-glucose cotransporter 2 inhibitors (SGLT2i) were originally developed as a novel oral drug for patients with type 2 diabetes mellitus. Unexpectedly, recent studies have shown that, beyond their effect on hyperglycemia, SGLT2i also have a variety of beneficial effects on cardiovascular disease. Experimental models of cardiovascular disease have shown that SGLT2i ameliorate the process of aging-related cardiovascular disease by inhibiting inflammation, reducing oxidative stress, and reversing endothelial dysfunction. In this review, we discuss the role of SGLT2i in aging-related cardiovascular disease and propose the use of SGLT2i to prevent and treat these conditions in older adults.

Proteomic sequencing analysis in a rat model of atrial fibrosis caused by chronic intermittent hypoxia

Background

Atrial fibrosis caused by long-term atrial fibrillation influences the outcomes of clinical treatment. An improved understanding of the mechanisms underlying atrial fibrillation may reveal new therapeutic targets. This study was conducted to analyze the changes in protein levels in the atrial tissue of a rat model of atrial fibrillation based on proteome sequencing.

Methods

Sprague-Dawley rats were used to develop a model of atrial fibrillation induced by chronic intermittent hypoxia (CIH). Histopathological changes were detected using hematoxylin and eosin staining and Masson's staining, and immunohistochemistry and western blotting for the levels of fibrosis biomarkers. Atrial fibrosis tissue samples were also evaluated by proteome sequencing. Differentially expressed proteins (DEPs) between the CIH and control groups were evaluated in functional assay. The expression levels of several key proteins were validated using western blotting.

Results

CIH resulted in atrial fibrosis and induced atrial fibrillation. We identified 145 DEPs between the CIH and control groups. These included Myh7, Myl2, Myl3, and Atpla3, which are involved in signaling pathways related to hypertrophic cardiomyopathy, glycerolipid metabolism, and cardiac muscle contraction. Western blotting revealed the upregulation of Myh7, Myl2, and Myl3 and the downregulation of Atpla3 in the CIH group compared with the control group. These results were consistent with the sequencing results.

Conclusions

Myh7, Myl2, Myl3, and Atpla3 may play key roles in the progression of atrial fibrillation through their involvement in cardiovascular-disease-related signaling pathways.

Circulating Total Extracellular Vesicles Cargo Are Associated with Age-Related Oxidative Stress and Susceptibility to Cardiovascular Diseases: Exploratory Results from Microarray Data

Aging is a risk factor for many non-communicable diseases such as cardiovascular and neurodegenerative diseases. Extracellular vesicles and particles (EVP) carry microRNAs that may play a role in age-related diseases and may induce oxidative stress. We hypothesized that aging could impact EVP miRNA and impair redox homeostasis, contributing to chronic age-related diseases. Our aims were to investigate the microRNA profiles of circulating total EVPs from aged and young adult animals and to evaluate the pro- and antioxidant machinery in circulating total EVPs. Plasma from 3- and 21-month-old male Wistar rats were collected, and total EVPs were isolated. MicroRNA isolation and microarray expression analysis were performed on EVPs to determine the predicted regulation of targeted mRNAs. Thirty-one mature microRNAs in circulating EVPs were impacted by age and were predicted to target molecules in canonical pathways directly related to cardiovascular diseases and oxidative status. Circulating total EVPs from aged rats had significantly higher NADPH oxidase levels and myeloperoxidase activity, whereas catalase activity was significantly reduced in EVPs from aged animals. Our data shows that circulating total EVP cargo-specifically microRNAs and oxidative enzymes-are involved in redox imbalance in the aging process and can potentially drive cardiovascular aging and, consequently, cardiac disease.

Protein kinase A: A potential marker of sympathovagal imbalance in heart failure

Mitigation of cardiac autonomic dysregulation by neuromodulation technologies is emerging as a new therapeutic modality of heart failure (HF). This recent progress has necessitated the identification of a biomarker for the quantification of sympathovagal balance, the potential target of 'neuromodulation' strategies. The currently available autonomic nervous system assessment parameters do not truly reflect the sympathovagal balance of the ventricle. Protein kinase A (PKA) is an intracellular enzyme that plays a major role in the pathophysiology of functional and structural ventricular remodeling in HF. Interestingly, sympathetic and parasympathetic activations exert reciprocal influence on the activity of PKA. The current review attempts to evaluate the potential concept and feasibility of using in vitro assessment of PKA activity as a marker of sympathovagal balance in HF.

The Sympathetic Nervous System in Hypertensive Heart Failure with Preserved LVEF

The neurohormonal model of heart failure (HF) pathogenesis states that a reduction in cardiac output caused by cardiac injury results in sympathetic nervous system (SNS) activation, that is adaptive in the short-term and maladaptive in the long-term. This model has proved extremely valid and has been applied in HF with a reduced left ventricular (LV) ejection fraction (LVEF). In contrast, it has been undermined in HF with preserved LVEF (HFpEF), which is due to hypertension (HTN) in the vast majority of the cases. Erroneously, HTN, which is the leading cause of cardiovascular disease and premature death worldwide and is present in more than 90% of HF patients, is tightly linked with SNS overactivity. In this paper we provide a contemporary overview of the contribution of SNS overactivity to the development and progression of hypertensive HF (HHF) as well as the clinical implications resulting from therapeutic interventions modifying SNS activity. Throughout the manuscript the terms HHF with preserved LVEF and HfpEF will be used interchangeably, considering that the findings in most HFpEF studies are driven by HTN.

7-Hydroxy Frullanolide Ameliorates Isoproterenol-Induced Myocardial Injury through Modification of iNOS and Nrf2 Genes

Myocardial infarction (MI) is the principal cause of premature death. Protecting myocardium from ischemia is the main focus of intense research. 7-hydroxy frullanolide (7-HF) is a potent anti-inflammatory agent, showing its efficacy in different acute and chronic inflammatory disorders such as atherosclerosis, suggesting it can be a potential cardioprotective agent. For the induction of MI, Sprague-Dawley rats (n = 5) were administered isoproterenol (ISO) 85 mg/kg s.c at 24 h intervals for two days. The potential cardioprotective effect of 7-HF and its mechanisms were explored by in vivo and in vitro methods. 7-HF significantly prevented the extent of myocardial injury by decreasing the infarct size, preserving the histology of myocardial tissue, and reducing the release of cardiac biomarkers. Further, 7-HF increased the mRNA expression of cardioprotective gene Nrf2 and reduced the mRNA expression of iNOS. 7-HF also improved cardiac function by decreasing the cardiac workload through its negative chronotropic and negative ionotropic effect, as well as by reducing peripheral vascular resistance due to the inhibition of voltage-dependent calcium channels and the release of calcium from intracellular calcium stores. In conclusion, 7-HF showed cardioprotective effects in the MI model, which might be due to modulating the expression of iNOS and Nrf2 genes as well as improving cardiac functions.

Hemodynamic impact of ephedrine on hypotension during general anesthesia: a prospective cohort study on middle-aged and older patients

BACKGROUND

Ephedrine is a mixed α- and β-agonist vasopressor that is frequently used for the correction of hypotension during general anesthesia. β-responsiveness has been shown to decrease with age; therefore, this study aimed to determine whether aging would reduce the pressor effect of ephedrine on hypotension during general anesthesia.

METHODS

Seventy-five patients aged ≥ 45 years were included in this study, with 25 patients allocated to each of the three age groups: 45-64 years, 65-74 years, and ≥ 75 years. All patients received propofol, remifentanil, and rocuronium for the induction of general anesthesia, followed by desflurane and remifentanil. Cardiac output (CO) was estimated using esCCO technology. Ephedrine (0.1 mg/kg) was administered for the correction of hypotension. The primary and secondary outcome measures were changes in the mean arterial pressure (MAP) and CO, respectively, at 5 min after the administration of ephedrine.  RESULTS: The administration of ephedrine significantly increased MAP (p < 0.001, mean difference: 8.34 [95% confidence interval (CI), 5.95-10.75] mmHg) and CO (p < 0.001, mean difference: 7.43 [95% CI, 5.20-9.65] %) across all groups. However, analysis of variance revealed that the degree of elevation of MAP (F [2, 72] = 0.546, p = 0.581, η2 = 0.015 [95% CI, 0.000-0.089]) and CO (F [2, 72] = 2.023, p = 0.140, η2 = 0.053 [95% CI, 0.000-0.162]) did not differ significantly among the groups. Similarly, Spearman's rank correlation and multiple regression analysis revealed no significant relation between age and the changes in MAP or CO after the administration of ephedrine.

CONCLUSION

The administration of ephedrine significantly increased MAP and CO; however, no significant correlation with age was observed in patients aged > 45 years. These findings suggest that ephedrine is effective for the correction of hypotension during general anesthesia, even in elderly patients.

TRIAL REGISTRATION

UMIN-CTR (UMIN000045038; 02/08/2021).

Optogenetic manipulation of Gq- and Gi/o-coupled receptor signaling in neurons and heart muscle cells

G-protein-coupled receptors (GPCRs) transmit signals into cells depending on the G protein type. To analyze the functions of GPCR signaling, we assessed the effectiveness of animal G-protein-coupled bistable rhodopsins that can be controlled into active and inactive states by light application using zebrafish. We expressed Gq- and Gi/o-coupled bistable rhodopsins in hindbrain reticulospinal V2a neurons, which are involved in locomotion, or in cardiomyocytes. Light stimulation of the reticulospinal V2a neurons expressing Gq-coupled spider Rh1 resulted in an increase in the intracellular Ca2+ level and evoked swimming behavior. Light stimulation of cardiomyocytes expressing the Gi/o-coupled mosquito Opn3, pufferfish TMT opsin, or lamprey parapinopsin induced cardiac arrest, and the effect was suppressed by treatment with pertussis toxin or barium, suggesting that Gi/o-dependent regulation of inward-rectifier K+ channels controls cardiac function. These data indicate that these rhodopsins are useful for optogenetic control of GPCR-mediated signaling in zebrafish neurons and cardiomyocytes.

Nuclear proteostasis imbalance in laminopathy-associated premature aging diseases

Laminopathies are a group of rare genetic disorders with heterogeneous clinical phenotypes such as premature aging, cardiomyopathy, lipodystrophy, muscular dystrophy, microcephaly, epilepsy, and so on. The cellular phenomena associated with laminopathy invariably show disruption of nucleoskeleton of lamina due to deregulated expression, localization, function, and interaction of mutant lamin proteins. Impaired spatial and temporal tethering of lamin proteins to the lamina or nucleoplasmic aggregation of lamins are the primary molecular events that can trigger nuclear proteotoxicity by modulating differential protein-protein interactions, sequestering quality control proteins, and initiating a cascade of abnormal post-translational modifications. Clearly, laminopathic cells exhibit moderate to high nuclear proteotoxicity, raising the question of whether an imbalance in nuclear proteostasis is involved in laminopathic diseases, particularly in diseases of early aging such as HGPS and laminopathy-associated premature aging. Here, we review nuclear proteostasis and its deregulation in the context of lamin proteins and laminopathies.

CD44 regulates Epac1-mediated β-adrenergic-receptor-induced Ca2+-handling abnormalities: implication in cardiac arrhythmias

BACKGROUND

Sustained, chronic activation of β-adrenergic receptor (β-AR) signaling leads to cardiac arrhythmias, with exchange proteins directly activated by cAMP (Epac1 and Epac2) as key mediators. This study aimed to evaluate whether CD44, a transmembrane receptor mediating various cellular responses, participates in Epac-dependent arrhythmias.

METHODS

The heart tissue from CD44 knockout (CD44-/-) mice, cultured HL-1 myocytes and the tissue of human ventricle were used for western blot, co-immunoprecipitaiton and confocal studies. Line-scanning confocal imaging was used for the study of cellular Ca2+ sparks on myocytes. Optical mapping and intra-cardiac pacing were applied for arrhythmia studies on mice's hearts.

RESULTS

In mice, isoproterenol, a β-AR agonist, upregulated CD44 and Epac1 and increased the association between CD44 and Epac1. Isoproterenol upregulated the expression of phospho-CaMKII (p-CaMKII), phospho-ryanodine receptor (p-RyR), and phospho-phospholamban (p-PLN) in mice and cultured myocytes; these effects were attenuated in CD44-/- mice compared with wild-type controls. In vitro, isoproterenol, 8-CPT-cAMP (an Epac agonist), and osteopontin (a ligand of CD44) significantly upregulated the expression of p-CaMKII, p-RyR, and p-PLN; this effect was attenuated by CD44 small interfering RNA (siRNA). In myocytes, resting Ca2+ sparks were induced by isoproterenol and overexpressed CD44, which were prevented by inhibiting CD44. Ex vivo optical mapping and in vivo intra-cardiac pacing studies showed isoproterenol-induced triggered events and arrhythmias in ventricles were prevented in CD44-/- mice. The inducibility of ventricular arrhythmias (VAs) was attenuated in CD44-/- HF mice compared with wild-type HF controls. In patients, CD44 were upregulated, and the association between CD44 and Epac1 were increased in ventricles with reduced contractility.

CONCLUSION

CD44 regulates β-AR- and Epac1-mediated Ca2+-handling abnormalities and VAs. Inhibition of CD44 is effective in reducing VAs in HF, which is potentially a novel therapeutic target for preventing the arrhythmias and sudden cardiac death in patients with diseased hearts.

IFN-γ and androgens disrupt mitochondrial function in murine myocytes

The effect of cytokines on non-traditional immunological targets under conditions of chronic inflammation is an ongoing subject of study. Fatigue is a symptom often associated with autoimmune diseases. Chronic inflammatory response and activated cell-mediated immunity are associated with cardiovascular myopathies which can be driven by muscle weakness and fatigue. Thus, we hypothesize that immune dysfunction-driven changes in myocyte mitochondria may play a critical role in fatigue-related pathogenesis. We show that persistent low-level expression of IFN-γ in designated IFN-γ AU-Rich Element deletion mice (ARE mice) under androgen exposure resulted in mitochondrial and metabolic deficiencies in myocytes from male or castrated ARE mice. Most notably, echocardiography unveiled that low ejection fraction in the left ventricle post-stress correlated with mitochondrial deficiencies, explaining how heart function decreases under stress. We report that inefficiencies and structural changes in mitochondria, with changes to expression of mitochondrial genes, are linked to male-biased fatigue and acute cardiomyopathy under stress. Our work highlights how male androgen hormone backgrounds and active autoimmunity reduce mitochondrial function and the ability to cope with stress and how pharmacological blockade of stress signal protects heart function. These studies provide new insight into the diverse actions of IFN-γ in fatigue, energy metabolism, and autoimmunity. © 2023 The Pathological Society of Great Britain and Ireland. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Regression of cardiac hypertrophy in health and disease: mechanisms and therapeutic potential

Left ventricular hypertrophy is a leading risk factor for cardiovascular morbidity and mortality. Although reverse ventricular remodelling was long thought to be irreversible, evidence from the past three decades indicates that this process is possible with many existing heart disease therapies. The regression of pathological hypertrophy is associated with improved cardiac function, quality of life and long-term health outcomes. However, less than 50% of patients respond favourably to most therapies, and the reversibility of remodelling is influenced by many factors, including age, sex, BMI and disease aetiology. Cardiac hypertrophy also occurs in physiological settings, including pregnancy and exercise, although in these cases, hypertrophy is associated with normal or improved ventricular function and is completely reversible postpartum or with cessation of training. Studies over the past decade have identified the molecular features of hypertrophy regression in health and disease settings, which include modulation of protein synthesis, microRNAs, metabolism and protein degradation pathways. In this Review, we summarize the evidence for hypertrophy regression in patients with current first-line pharmacological and surgical interventions. We further discuss the molecular features of reverse remodelling identified in cell and animal models, highlighting remaining knowledge gaps and the essential questions for future investigation towards the goal of designing specific therapies to promote regression of pathological hypertrophy.

Age-Dependent Changes in Calcium Regulation after Myocardial Ischemia-Reperfusion Injury

During aging, heart structure and function gradually deteriorate, which subsequently increases susceptibility to ischemia-reperfusion (IR). Maintenance of Ca²⁺ homeostasis is critical for cardiac contractility. We used Langendorff's model to monitor the susceptibility of aging (6-, 15-, and 24-month-old) hearts to IR, with a specific focus on Ca²⁺-handling proteins. IR, but not aging itself, triggered left ventricular changes when the maximum rate of pressure development decreased in 24-month-olds, and the maximum rate of relaxation was most affected in 6-month-old hearts. Aging caused a deprivation of Ca²⁺-ATPase (SERCA2a), Na⁺/Ca²⁺ exchanger, mitochondrial Ca²⁺ uniporter, and ryanodine receptor contents. IR-induced damage to ryanodine receptor stimulates Ca²⁺ leakage in 6-month-old hearts and elevated phospholamban (PLN)-to-SERCA2a ratio can slow down Ca²⁺ reuptake seen at 2-5 μM Ca²⁺. Total and monomeric PLN mirrored the response of overexpressed SERCA2a after IR in 24-month-old hearts, resulting in stable Ca²⁺-ATPase activity. Upregulated PLN accelerated inhibition of Ca²⁺-ATPase activity at low free Ca²⁺ in 15-month-old after IR, and reduced SERCA2a content subsequently impairs the Ca²⁺-sequestering capacity. In conclusion, our study suggests that aging is associated with a significant decrease in the abundance and function of Ca²⁺-handling proteins. However, the IR-induced damage was not increased during aging.

Mitochondrial miRNA as epigenomic signatures: Visualizing aging-associated heart diseases through a new lens

Aging bears many hard knocks, but heart disorders earn a particular allusion, being the most widespread. Cardiovascular diseases (CVDs) are becoming the biggest concern to mankind due to sundry health conditions directly or indirectly related to heart-linked abnormalities. Scientists know that mitochondria play a critical role in the pathophysiology of cardiac diseases. Both environment and genetics play an essential role in modulating and controlling mitochondrial functions. Even a minor abnormality may prove detrimental to heart function. Advanced age combined with an unhealthy lifestyle can cause most cardiomyocytes to be replaced by fibrotic tissue which upsets the conducting system and leads to arrhythmias. An aging heart encounters far more heart-associated comorbidities than a young heart. Many state-of-the-art technologies and procedures are already being used to prevent and treat heart attacks worldwide. However, it remains a mystery when this heart bomb would explode because it lacks an alarm. This calls for a novel and effective strategy for timely diagnosis and a sure-fire treatment. This review article provides a comprehensive overture of prospective potentials of mitochondrial miRNAs that predict complicated and interconnected pathways concerning heart ailments and signature compilations of relevant miRNAs as biomarkers to plot the role of miRNAs in epigenomics. This article suggests that analysis of DNA methylation patterns in age-associated heart diseases may determine age-impelled biomarkers of heart disease.

Metabolic Changes in Cardiac Aging

Cardiac aging is a natural process accompanied by cardiomyocyte hypertrophy and dysfunction. These changes can lead to adverse organ remodeling and ultimately lead to the development of heart failure. The study of cardiac aging is helpful to explore the mechanism of senescence and is of great significance for preventing cardiac aging. Cardiac aging is accompanied by changes in various metabolic functions. In this process, due to the change of metabolic substrates and enzyme activities, oxidative stress response increases, and reactive oxygen species (ROS) increases, accompanied by mitochondrial dysfunction and gene expression changes, so related protein metabolism also changes. Hormone metabolism and autophagy are also involved in the process of cardiac aging. Based on these findings, changes in diet, caloric restriction, improvement of mitochondrial function and promotion of autophagy have been proven to have positive effects in delaying cardiac aging. This article reviews the metabolic changes involved in the process of cardiac aging from different aspects, and briefly reviews the measures to improve cardiac aging.

Investigating microRNAs in diabetic cardiomyopathy as tools for early detection and therapeutics

To profile microRNAs population of glucose-induced cardiomyoblast cell line and identify the differentially expressed microRNAs and their role under pre-diabetes and diabetes condition in vitro. Rat fetal ventricular cardiomyoblast cell line H9c2 was treated with D-glucose to mimic pre-diabetic, diabetic, and high-glucose conditions. Alteration in cellular, nuclear morphology, and change in ROS generation was analyzed through fluorescent staining. Small RNA sequencing was performed using Illumina NextSeq 550 sequencer and was validated using stem-loop qRT-PCR. A large number (~ 100) differential miRNAs were detected in each treated samples as compared to control; however, a similar expression pattern was observed between pre-diabetes and diabetes conditions with the exception for miR-429, miR-101b-5p, miR-503-3p, miR-384-5p, miR-412-5p, miR-672-5p, and miR-532-3p. Functional annotation of differential expressed target genes revealed their involvement in significantly enriched key pathways associated with diabetic cardiomyopathy. For the first time, we report the differential expression of miRNAs (miR-1249, miR-3596d, miR- 3586-3p, miR-7b-3p, miR-191, miR-330-3p, miR-328a, let7i-5p, miR-146-3p, miR-26a-3p) in diabetes-induced cardiac cells. Hyperglycemia threatens the cell homeostasis by dysregulation of miRNAs that begins at a glucose level 10 mM and remains undetected. Analysis of differential expressed miRNAs in pre-diabetes and diabetes conditions and their role in regulatory mechanisms of diabetic cardiomyopathy holds high potential in the direction of using miRNAs as minimally invasive diagnostic and therapeutic tools.