Translating Translation to Mechanisms of Cardiac Hypertrophy

Viral Infection and Connexin Dysfunction in the Heart

PURPOSE OF REVIEW

Gap junctions, comprising connexin proteins, enable the direct intercellular electrical coupling of cardiomyocytes, and disruption of this process is arrhythmogenic. In addition, gap junctions effect metabolic coupling and of relevance to this review, propagate host antiviral immune responses. Accordingly, connexins have emerged as viral targets during infection. This review summarizes current knowledge regarding contributions of inflammation vs virally encoded factors in driving alterations to cardiac gap junction function.

RECENT FINDINGS

In addition to host immune-mediated effects on cardiac electrophysiology and gap junctions in myocarditis, there is now increasing appreciation for virally encoded factors targeting connexin function in acute/active infection. We now know diverse viral species have independently evolved to directly target connexin function during infection. Understanding both the direct and indirect effects of viral infection on cardiac gap junctions is critical to inform treatment strategies and development of novel therapeutics for acute infection as a distinct disease process from chronic myocarditis.

NAD+ enhancers as therapeutic agents in the cardiorenal axis

Cardiorenal diseases represent a complex interplay between heart failure and renal dysfunction, being clinically classified as cardiorenal syndromes (CRS). Recently, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism, through deficient NAD+ synthesis and/or elevated consumption, have proved to be decisive in the onset and progress of cardiorenal disease. NAD+ is a pivotal coenzyme in cellular metabolism, being significant in various signaling pathways, such as energy metabolism, DNA damage repair, gene expression, and stress response. Convincing evidence suggests that strategies designed to boost cellular NAD+ levels are a promising therapeutic option to address cardiovascular and renal disorders. Here, we review and discuss the implications of NAD+ metabolism in cardiorenal diseases, focusing on the propitious NAD+ boosting therapeutic strategies, based on the use of NAD+ precursors, poly(ADP-ribose) polymerase inhibitors, sirtuin activators, and other alternative approaches, such as CD38 blockade, nicotinamide phosphoribosyltransferase activation and combined interventions.

RNA binding proteins in cardiovascular development and disease

Congenital heart disease (CHD) is the most common birth defect affecting>1.35 million newborn babies worldwide. CHD can lead to prenatal, neonatal, postnatal lethality or life-long cardiac complications. RNA binding protein (RBP) mutations or variants are emerging as contributors to CHDs. RBPs are wizards of gene regulation and are major contributors to mRNA and protein landscape. However, not much is known about RBPs in the developing heart and their contributions to CHD. In this chapter, we will discuss our current knowledge about specific RBPs implicated in CHDs. We are in an exciting era to study RBPs using the currently available and highly successful RNA-based therapies and methodologies. Understanding how RBPs shape the developing heart will unveil their contributions to CHD. Identifying their target RNAs in the embryonic heart will ultimately lead to RNA-based treatments for congenital heart disease.

Identification of FDA-approved drugs that induce heart regeneration in mammals

Targeting Meis1 and Hoxb13 transcriptional activity could be a viable therapeutic strategy for heart regeneration. In this study, we performd an in silico screening to identify FDA-approved drugs that can inhibit Meis1 and Hoxb13 transcriptional activity based on the resolved crystal structure of Meis1 and Hoxb13 bound to DNA. Paromomycin (Paro) and neomycin (Neo) induced proliferation of neonatal rat ventricular myocytes in vitro and displayed dose-dependent inhibition of Meis1 and Hoxb13 transcriptional activity by luciferase assay and disruption of DNA binding by electromobility shift assay. X-ray crystal structure revealed that both Paro and Neo bind to Meis1 near the Hoxb13-interacting domain. Administration of Paro-Neo combination in adult mice and in pigs after cardiac ischemia/reperfusion injury induced cardiomyocyte proliferation, improved left ventricular systolic function and decreased scar formation. Collectively, we identified FDA-approved drugs with therapeutic potential for induction of heart regeneration in mammals.

How does NFAT3 regulate the occurrence of cardiac hypertrophy?

Cardiac hypertrophy is initially an adaptive response to physiological and pathological stimuli. Although pathological myocardial hypertrophy is the main cause of morbidity and mortality, our understanding of its mechanism is still weak. NFAT3 (nuclear factor of activated T-cell-3) is a member of the nuclear factor of the activated T cells (NFAT) family. NFAT3 plays a critical role in regulating the expression of cardiac hypertrophy genes by inducing their transcription. Recently, accumulating evidence has indicated that NFAT3 is a potent regulator of the progression of cardiac hypertrophy. This review, for the first time, summarizes the current studies on NFAT3 in cardiac hypertrophy, including the pathophysiological processes and the underlying pathological mechanism, focusing on the nuclear translocation and transcriptional function of NFAT3. This review will provide deep insight into the pathogenesis of cardiac hypertrophy and a theoretical basis for identifying new therapeutic targets in the NFAT3 network.

Ribosome biogenesis in disease: new players and therapeutic targets

The ribosome is a multi-unit complex that translates mRNA into protein. Ribosome biogenesis is the process that generates ribosomes and plays an essential role in cell proliferation, differentiation, apoptosis, development, and transformation. The mTORC1, Myc, and noncoding RNA signaling pathways are the primary mediators that work jointly with RNA polymerases and ribosome proteins to control ribosome biogenesis and protein synthesis. Activation of mTORC1 is required for normal fetal growth and development and tissue regeneration after birth. Myc is implicated in cancer development by enhancing RNA Pol II activity, leading to uncontrolled cancer cell growth. The deregulation of noncoding RNAs such as microRNAs, long noncoding RNAs, and circular RNAs is involved in developing blood, neurodegenerative diseases, and atherosclerosis. We review the similarities and differences between eukaryotic and bacterial ribosomes and the molecular mechanism of ribosome-targeting antibiotics and bacterial resistance. We also review the most recent findings of ribosome dysfunction in COVID-19 and other conditions and discuss the consequences of ribosome frameshifting, ribosome-stalling, and ribosome-collision. We summarize the role of ribosome biogenesis in the development of various diseases. Furthermore, we review the current clinical trials, prospective vaccines for COVID-19, and therapies targeting ribosome biogenesis in cancer, cardiovascular disease, aging, and neurodegenerative disease.

Importance of NAD+ Anabolism in Metabolic, Cardiovascular and Neurodegenerative Disorders

The role of nicotinamide adenine dinucleotide (NAD+) in ageing has emerged as a critical factor in understanding links to a wide range of chronic diseases. Depletion of NAD+, a central redox cofactor and substrate of numerous metabolic enzymes, has been detected in many major age-related diseases. However, the mechanisms behind age-associated NAD+ decline remains poorly understood. Despite limited conclusive evidence, supplements aimed at increasing NAD+ levels are becoming increasingly popular. This review provides renewed insights regarding the clinical utility and benefits of NAD+ precursors, namely nicotinamide (NAM), nicotinic acid (NA), nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), in attenuating NAD+ decline and phenotypic characterization of age-related disorders, including metabolic, cardiovascular and neurodegenerative diseases. While it is anticipated that NAD+ precursors can play beneficial protective roles in several conditions, they vary in their ability to promote NAD+ anabolism with differing adverse effects. Careful evaluation of the role of NAD⁺, whether friend or foe in ageing, should be considered.

Gap Junctions and Ageing

Gap junctions, comprising connexin proteins, create conduits directly coupling the cytoplasms of adjacent cells. Expressed in essentially all tissues, dynamic gap junction structures enable the exchange of small molecules including ions and second messengers, and are central to maintenance of homeostasis and synchronized excitability. With such diverse and critical roles throughout the body, it is unsurprising that alterations to gap junction and/or connexin expression and function underlie a broad array of age-related pathologies. From neurological dysfunction to cardiac arrhythmia and bone loss, it is hard to identify a human disease state that does not involve reduced, or in some cases inappropriate, intercellular communication to affect organ function. With a complex life cycle encompassing several key regulatory steps, pathological gap junction remodeling during ageing can arise from alterations in gene expression, translation, intracellular trafficking, and posttranslational modification of connexins. Connexin proteins are now known to "moonlight" and perform a variety of non-junctional functions in the cell, independent of gap junctions. Furthermore, connexin "hemichannels" on the cell surface can communicate with the extracellular space without ever coupling to an adjacent cell to form a gap junction channel. This chapter will focus primarily on gap junctions in ageing, but such non-junctional connexin functions will be referred to where appropriate and the full spectrum of connexin biology should be noted as potentially causative/contributing to some findings in connexin knockout animals, for example.

PHEVIR: an artificial intelligence algorithm that predicts the molecular role of pathogens in complex human diseases

Infectious diseases are known to cause a wide variety of post-infection complications. However, it's been challenging to identify which diseases are most associated with a given pathogen infection. Using the recently developed LeMeDISCO approach that predicts comorbid diseases associated with a given set of putative mode of action (MOA) proteins and pathogen-human protein interactomes, we developed PHEVIR, an algorithm which predicts the corresponding human disease comorbidities of 312 viruses and 57 bacteria. These predictions provide an understanding of the molecular bases of complications and means of identifying appropriate drug targets to treat them. As an illustration of its power, PHEVIR is applied to identify putative driver pathogens and corresponding human MOA proteins for Type 2 diabetes, atherosclerosis, Alzheimer's disease, and inflammatory bowel disease. Additionally, we explore the origins of the oncogenicity/oncolyticity of certain pathogens and the relationship between heart disease and influenza. The full PHEVIR database is available at https://sites.gatech.edu/cssb/phevir/ .

METTL3 mediates Ang-II-induced cardiac hypertrophy through accelerating pri-miR-221/222 maturation in an m6A-dependent manner

Background

METTL3 is the core catalytic enzyme in m6A and is involved in a variety of cardiovascular diseases. However, whether and how METTL3 plays a role during angiotensin II (Ang-II)-induced myocardial hypertrophy is still unknown.

Methods

Neonatal rat cardiomyocytes (NRCMs) and C57BL/6J mice were treated with Ang-II to induce myocardial hypertrophy. qRT-PCR and western blots were used to detect the expression of RNAs and proteins. Gene function was verified by knockdown and/or overexpression, respectively. Luciferase and RNA immunoprecipitation (RIP) assays were used to verify interactions among multiple genes. Wheat germ agglutinin (WGA), hematoxylin and eosin (H&E), and immunofluorescence were used to examine myocardial size. m6A methylation was detected by a colorimetric kit.

Results

METTL3 and miR-221/222 expression and m6A levels were significantly increased in response to Ang-II stimulation. Knockdown of METTL3 or miR-221/222 could completely abolish the ability of NRCMs to undergo hypertrophy. The expression of miR-221/222 was positively regulated by METTL3, and the levels of pri-miR-221/222 that bind to DGCR8 or form m6A methylation were promoted by METTL3 in NRCMs. The effect of METTL3 knockdown on hypertrophy was antagonized by miR-221/222 overexpression. Mechanically, Wnt/β-catenin signaling was activated during hypertrophy and restrained by METTL3 or miR-221/222 inhibition. The Wnt/β-catenin antagonist DKK2 was directly targeted by miR-221/222, and the effect of miR-221/222 inhibitor on Wnt/β-catenin was abolished after inhibition of DKK2. Finally, AAV9-mediated cardiac METTL3 knockdown was able to attenuate Ang-II-induced cardiac hypertrophy in mouse model.

Conclusions

Our findings suggest that METTL3 positively modulates the pri-miR221/222 maturation process in an m6A-dependent manner and subsequently activates Wnt/β-catenin signaling by inhibiting DKK2, thus promoting Ang-II-induced cardiac hypertrophy. AAV9-mediated cardiac METTL3 knockdown could be a therapeutic for pathological myocardial hypertrophy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00349-1.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

Nicotinamide Riboside Alleviates Cardiac Dysfunction and Remodeling in Pressure Overload Cardiac Hypertrophy

Background

Cardiac hypertrophy is a compensatory response to pressure overload, which eventually leads to heart failure. The current study explored the protective effect of nicotinamide riboside (NR), a NAD⁺ booster that may be administered through the diet, on the occurrence of myocardial hypertrophy and revealed details of its underlying mechanism.

Methods

Transverse aortic constriction (TAC) surgery was performed to establish a murine model of myocardial hypertrophy. Mice were randomly divided into four groups: sham, TAC, sham+NR, and TAC+NR. NR treatment was given daily by oral gavage. Cardiac structure and function were assessed using small animal echocardiography. Mitochondrial oxidative stress was evaluated by dihydroethidium (DHE) staining, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity. Levels of expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), IL-1β, TNF-α, and Sirtuin3 were measured by real-time PCR and ELISA. Expression levels of Caspase-1, Caspase-1 pro, cleaved Gasdermin D (GSDMD), NLRP3, ASC, Sirtuin3, ac-MnSOD, and total MnSOD were measured by Western blot.

Results

Reductions in the heart/body mass ratio (HW/BW) and lung/body mass ratio (LW/BW) and in ANP, BNP, and LDH levels were observed in the TAC group on the administration of NR (P < 0.05). Moreover, echocardiography data showed that cardiac dysfunction and structural changes caused by TAC were improved by NR treatment (P < 0.05). NR treatment also reduced levels of the inflammatory cytokines, IL-1β and TNF-α, and attenuated activation of NLRP3 inflammasomes induced by TAC. Furthermore, changes in DHE staining, MDA content, and SOD activity indicated that NR treatment alleviated the oxidative stress caused by TAC. Data from ELISA and Western blots revealed elevated myocardial NAD⁺ content and Sirtuin3 activity and decreased acetylation of MnSOD after NR treatment, exposing aspects of the underlying signaling pathway.

Conclusion

NR treatment alleviated TAC-induced pathological cardiac hypertrophy and dysfunction. Mechanically, these beneficial effects were attributed to the inhibition of NLRP3 inflammasome activation and myocardial inflammatory response by regulating the NAD⁺-Sirtuin3-MnSOD signaling pathway.

The function of LncRNA-H19 in cardiac hypertrophy

Cardiac hypertrophy, characterized by the enlargement of cardiomyocytes, is initially an adaptive response to physiological and pathological stimuli. Decompensated cardiac hypertrophy is related to fibrosis, inflammatory cytokine, maladaptive remodeling, and heart failure. Although pathological myocardial hypertrophy is the main cause of hypertrophy-related morbidity and mortality, our understanding of its mechanism is still poor. Long noncoding RNAs (lncRNAs) are noncoding RNAs that regulate various physiological and pathological processes through multiple molecular mechanisms. Recently, accumulating evidence has indicated that lncRNA-H19 is a potent regulator of the progression of cardiac hypertrophy. For the first time, this review summarizes the current studies about the role of lncRNA-H19 in cardiac hypertrophy, including its pathophysiological processes and underlying pathological mechanism, including calcium regulation, fibrosis, apoptosis, angiogenesis, inflammation, and methylation. The context within which lncRNA-H19 might be developed as a target for cardiac hypertrophy treatment is then discussed to gain better insight into the possible biological functions of lncRNA-H19 in cardiac hypertrophy.

Ginkgolide B Protects Cardiomyocytes from Angiotensin II-Induced Hypertrophy via Regulation of Autophagy through SIRT1-FoxO1

Ginkgolide B (GB) is an active ingredient extracted from Ginkgo biloba leaves. However, the effects of GB on cardiac hypertrophy remain unclear. The study is aimed at determining whether GB could alleviate cardiac hypertrophy and exploring its underlying molecular mechanism. Rat cardiomyocyte cell line H9c2 cells were pretreated with GB and incubated with angiotensin II (Ang II) to simulate an in vitro cardiac hypertrophy model. Cell viability, cell size, hypertrophy markers, and autophagy were determined in H9c2 cells after Ang II treatment. Proteins involved in autophagy and the SIRT1 pathway were determined by western blot. Our data demonstrated that GB attenuated Ang II-induced cardiac hypertrophy and reduced the mRNA expressions of hypertrophy marker, atrial natriuretic peptide (ANP), and β-myosin heavy chain (β-MHC). GB further increased Ang II-induced autophagy in H9c2 cells and modulated expressions of autophagy-related proteins Beclin1 and P62. Modulation of autophagy using autophagy inhibitor 3-methyladenine (3-MA) could abrogate GB-downregulated transcription of NPPA. We then showed that GB attenuated Ang II-induced oxidative stress and reduction in SIRT1 and FoxO1 protein expression. Finally, the effect of GB on autophagy and cardiac hypertrophy could be reversed by SIRT1 inhibitor EX-527. GB inhibits Ang II-induced cardiac hypertrophy by enhancing autophagy via the SIRT1-FoxO1 signaling pathway and might be a potential agent in treating pathological cardiac hypertrophy.

Mass Spectrometry-Based Redox and Protein Profiling of Failing Human Hearts

Oxidative stress contributes to detrimental functional decline of the myocardium, leading to the impairment of the antioxidative defense, dysregulation of redox signaling, and protein damage. In order to precisely dissect the changes of the myocardial redox state correlated with oxidative stress and heart failure, we subjected left-ventricular tissue specimens collected from control or failing human hearts to comprehensive mass spectrometry-based redox and quantitative proteomics, as well as glutathione status analyses. As a result, we report that failing hearts have lower glutathione to glutathione disulfide ratios and increased oxidation of a number of different proteins, including constituents of the contractile machinery as well as glycolytic enzymes. Furthermore, quantitative proteomics of failing hearts revealed a higher abundance of proteins responsible for extracellular matrix remodeling and reduced abundance of several ion transporters, corroborating contractile impairment. Similar effects were recapitulated by an in vitro cell culture model under a controlled oxygen atmosphere. Together, this study provides to our knowledge the most comprehensive report integrating analyses of protein abundance and global and peptide-level redox state in end-stage failing human hearts as well as oxygen-dependent redox and global proteome profiles of cultured human cardiomyocytes.

Translation Regulation by eIF2α Phosphorylation and mTORC1 Signaling Pathways in Non-Communicable Diseases (NCDs)

Non-communicable diseases (NCDs) are medical conditions that, by definition, are non-infectious and non-transmissible among people. Much of current NCDs are generally due to genetic, behavioral, and metabolic risk factors that often include excessive alcohol consumption, smoking, obesity, and untreated elevated blood pressure, and share many common signal transduction pathways. Alterations in cell and physiological signaling and transcriptional control pathways have been well studied in several human NCDs, but these same pathways also regulate expression and function of the protein synthetic machinery and mRNA translation which have been less well investigated. Alterations in expression of specific translation factors, and disruption of canonical mRNA translational regulation, both contribute to the pathology of many NCDs. The two most common pathological alterations that contribute to NCDs discussed in this review will be the regulation of eukaryotic initiation factor 2 (eIF2) by the integrated stress response (ISR) and the mammalian target of rapamycin complex 1 (mTORC1) pathways. Both pathways integrally connect mRNA translation activity to external and internal physiological stimuli. Here, we review the role of ISR control of eIF2 activity and mTORC1 control of cap-mediated mRNA translation in some common NCDs, including Alzheimer’s disease, Parkinson’s disease, stroke, diabetes mellitus, liver cirrhosis, chronic obstructive pulmonary disease (COPD), and cardiac diseases. Our goal is to provide insights that further the understanding as to the important role of translational regulation in the pathogenesis of these diseases.

Cardiotoxicity and Heart Failure: Lessons from Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes and Anticancer Drugs

Human-induced pluripotent stem cells (hiPSCs) are discussed as disease modeling for optimization and adaptation of therapy to each individual. However, the fundamental question is still under debate whether stem-cell-based disease modeling and drug discovery are applicable for recapitulating pathological processes under in vivo conditions. Drug treatment and exposure to different chemicals and environmental factors can initiate diseases due to toxicity effects in humans. It is well documented that drug-induced cardiotoxicity accelerates the development of heart failure (HF). Until now, investigations on the understanding of mechanisms involved in HF by anticancer drugs are hindered by limitations of the available cellular models which are relevant for human physiology and by the fact that the clinical manifestation of HF often occurs several years after its initiation. Recently, we identified similar genomic biomarkers as observed by HF after short treatment of hiPSCs-derived cardiomyocytes (hiPSC-CMs) with different antitumor drugs such as anthracyclines and etoposide (ETP). Moreover, we identified common cardiotoxic biological processes and signal transduction pathways which are discussed as being crucial for the survival and function of cardiomyocytes and, therefore, for the development of HF. In the present review, I discuss the applicability of the in vitro cardiotoxicity test systems as modeling for discovering preventive mechanisms/targets against cardiotoxicity and, therefore, for novel HF therapeutic concepts.