The transcription factors GATA4 and GATA6 regulate cardiomyocyte hypertrophy in vitro and in vivo

A biodegradable, microstructured, electroconductive and nano-integrated drug eluting patch (MENDEP) for myocardial tissue engineering

We produced a microstructured, electroconductive and nano-functionalized drug eluting cardiac patch (MENDEP) designed to attract endogenous precursor cells, favor their differentiation and counteract adverse ventricular remodeling in situ. MENDEP showed mechanical anisotropy and biaxial strength comparable to porcine myocardium, reduced impedance, controlled biodegradability, molecular recognition ability and controlled drug release activity. In vitro, cytocompatibility and cardioinductivity were demonstrated. Migration tests showed the chemoattractive capacity of the patches and conductivity assays showed unaltered cell-cell interactions and cell beating synchronicity. MENDEP was then epicardially implanted in a rat model of ischemia/reperfusion (I/R). Histological, immunofluorescence and biomarker analysis indicated that implantation did not cause damage to the healthy myocardium. After I/R, MENDEP recruited precursor cells into the damaged myocardium and triggered their differentiation towards the vascular lineage. Under the patch, the myocardial tissue appeared well preserved and cardiac gap junctions were correctly distributed at the level of the intercalated discs. The fibrotic area measured in the I/R group was partially reduced in the patch group. Overall, these results demonstrate that MENDEP was fully retained on the epicardial surface of the left ventricle over 4-week implantation period, underwent progressive vascularization, did not perturb the healthy myocardium and showed great potential in repairing the infarcted area.

Targeting GATA6 with pedunculoside inhibits fetal gene expression to attenuate pathological cardiac hypertrophy

BACKGROUND

Pathological cardiac hypertrophy is a characteristic feature of numerous cardiovascular diseases and significantly impacts human health. However, effective treatment options for cardiac hypertrophy are still significantly unmet. Pedunculoside, a pentacyclic triterpenoid saponin from the traditional Chinese herb Ilex rotunda Thunb., exhibits various pharmacological properties such as anti-inflammatory and cardiovascular therapeutic effects, but its anti-hypertrophy efficacy and mechanisms have not yet been reported.

PURPOSE

This study aimed to confirm the ameliorating effect of pedunculoside on cardiac hypertrophy and elucidate its underlying mechanism.

METHODS

To investigate the effect of pedunculoside on cardiac hypertrophy, we used transverse aortic constriction (TAC) and isoproterenol hydrochloride (ISO) infusion to induce cardiac hypertrophy model in mice. Angiotensin II (Ang II) was used to mimic hypertrophy model in myocardial cells. Then, we utilized a biotin-tagged carabrone chemical probe and validation experiments to pinpoint pedunculoside's key targets. Further, molecular docking study and sites mutation were used to predict and identify the binding modes of pedunculoside to target. Finally, structural optimization was carried out to find new pedunculoside derivatives with stronger anti-hypertrophy activity and binding affinity to the target.

RESULTS

Our findings revealed for the first time that pedunculoside treatment significantly attenuated hypertrophic phenotypes in response to TAC and ISO. It also effectively reduced hypertrophy and fibrosis in myocardial cells exposed to Ang II stimulation. Mechanically, we identified transcription factor GATA-6 (GATA6) as a key target of pedunculoside for treating cardiac hypertrophy. Further studies demonstrated that pedunculoside blocks cardiac hypertrophy progression by inhibiting the transcriptional activation of GATA6 on promoting fetal gene expression. More importantly, a new pedunculoside derivative PE-3 with stronger anti-hypertrophy activity and affinity for GATA6 was discovered.

CONCLUSION

Our findings suggest that pedunculoside and PE-3 could be developed as promising drug candidates for cardiac hypertrophy treatment.

Molecular gatekeepers of endogenous adult mammalian cardiomyocyte proliferation

Irreversible cardiac fibrosis, cardiomyocyte death and chronic cardiac dysfunction after myocardial infarction pose a substantial global health-care challenge, with no curative treatments available. To regenerate the injured heart, cardiomyocytes must proliferate to replace lost myocardial tissue - a capability that adult mammals have largely forfeited to adapt to the demanding conditions of life. Using various preclinical models, our understanding of cardiomyocyte proliferation has progressed remarkably, leading to the successful reactivation of cell cycle induction in adult animals, with functional recovery after cardiac injury. Central to this success is the targeting of key pathways and structures that drive cardiomyocyte maturation after birth - nucleation and ploidy, sarcomere structure, developmental signalling, chromatin and epigenetic regulation, the microenvironment and metabolic maturation - forming a complex regulatory framework that allows efficient cellular contraction but restricts cardiomyocyte proliferation. In this Review, we explore the molecular pathways underlying these core mechanisms and how their manipulation can reactivate the cell cycle in cardiomyocytes, potentially contributing to cardiac repair.

Growth-Associated Protein-43 Loss Promotes Ca2+ and ROS Imbalance in Cardiomyocytes

Growth-Associated Protein-43 (GAP-43) is a calmodulin-binding protein, originally found in neurons, that in skeletal muscle regulates the handling of intracellular Ca2+ dynamics. According to its role in Ca2+ regulation, myotubes from GAP-43 knockout (GAP-43-/-) mice display alterations in spontaneous Ca2+ oscillations and increased Ca2+ release. The emerging hypothesis is that GAP-43 regulates CaM interactions with RyR and DHPR Ca2+ channels. The loss of GAP-43 promotes cardiac hypertrophy in newborn GAP-43-/- mice, extending the physiological role of GAP-43 in cardiac muscle. We investigated the role of GAP-43 in cardiomyocytes derived from the hearts of GAP-43-/- mice, evaluating intracellular Ca2+ variations and the correlation with the levels of reactive oxygen species (ROS), considering their importance in cardiovascular physiology. In GAP-43-/- cardiomyocytes, we found the increased expression of markers of cardiac hypertrophy, Ca2+ alterations, and high mitochondria ROS levels (O2•-) together with increased oxidized functional proteins. Treatment with a CaM inhibitor (W7) restored Ca2+ and ROS alterations, possibly due to high mitochondrial Ca2+ entry by a mitochondrial Ca2+ uniporter. Indeed, Ru360 was able to abolish O2•- mitochondrial production. Our results suggest that GAP-43 has a key role in the regulation of Ca2+ and ROS homeostasis, alterations to which could trigger heart disease.

Modeling the Interplay of Sex Hormones in Cardiac Hypertrophic Signaling

Biological sex plays a crucial role in the outcomes of cardiac health and therapies. Sex hormones are known to strongly influence cardiac remodeling through intracellular signaling pathways, yet their underlying mechanisms remain unclear. To address this need, we developed and validated a logic-based systems biology model of cardiomyocyte hypertrophy that, for the first time, incorporates the effects of both estradiol (E2) and testosterone (T) alongside well-established hypertrophic stimuli (Strain, angiotensin II (AngII), and endothelin-1 (ET-1)). We qualitatively validated the model to literature data with 84% agreement. Quantitative validation was done by simulating the impact of the inputs (E2, T, Strain, AngII, and ET-1) on cardiac hypertrophy, captured as change in CellArea. We perturbed the validated model to examine the differential response to hypertrophy and identify changes in influential and sensitive downstream nodes for a male, pre-menopausal female, and post-menopausal female condition. Our results suggest that T has a greater impact on hypertrophy than E2. This model increases our understanding of the mechanisms through which sex hormones influence cardiac hypertrophy and can aid with developing more effective cardiac therapies for all patients.

TongGuanWan Alleviates Doxorubicin- and Isoproterenol-Induced Cardiac Hypertrophy and Fibrosis by Modulating Apoptotic and Fibrotic Pathways

Heart failure, a major public health issue, often stems from prolonged stress or damage to the heart muscle, leading to cardiac hypertrophy. This can progress to heart failure and other cardiovascular problems. Doxorubicin (DOX), a common chemotherapy drug, and isoproterenol (ISO), a β-adrenergic agonist, both induce cardiac hypertrophy through different mechanisms. This study investigates TongGuanWan (TGW,), a traditional herbal remedy, for its effects on cardiac hypertrophy and fibrosis in DOX-induced H9c2 cells and ISO-induced mouse models. TGW was found to counteract DOX-induced increases in H9c2 cell surface area (n = 8, p < 0.01) and improve biomarkers like ANP (n = 3, p < 0.01)) and BNP (n = 3, p < 0.01). It inhibited the MAPK pathway (n = 4, p < 0.01) and GATA-4/calcineurin/NFAT-3 signaling, reduced inflammation by decreasing NF-κB p65 translocation, and enhanced apoptosis-related factors such as caspase-3 (n = 3, p < 0.01), caspase-9 (n = 3, p < 0.01), Bax (n = 3, p < 0.01), and Bcl-2 (n = 3, p < 0.01). Flow cytometry showed TGW reduced apoptotic cell populations. In vivo, TGW reduced heart (n = 8~10, p < 0.01), and left ventricle weights (n = 6~7), cardiac hypertrophy markers (n = 3, p < 0.01), and perivascular fibrosis in ISO-induced mice, with Western blot analysis confirming decreased levels of fibrosis-related factors like fibronectin, α-SMA (n = 3, p < 0.05), and collagen type I (n = 3, p < 0.05). These findings suggest TGW has potential as a therapeutic option for cardiac hypertrophy and fibrosis.

Neuraminidase-1 (NEU1): Biological Roles and Therapeutic Relevance in Human Disease

Neuraminidases catalyze the desialylation of cell-surface glycoconjugates and play crucial roles in the development and function of tissues and organs. In both physiological and pathophysiological contexts, neuraminidases mediate diverse biological activities via the catalytic hydrolysis of terminal neuraminic, or sialic acid residues in glycolipid and glycoprotein substrates. The selective modulation of neuraminidase activity constitutes a promising strategy for treating a broad spectrum of human pathologies, including sialidosis and galactosialidosis, neurodegenerative disorders, cancer, cardiovascular diseases, diabetes, and pulmonary disorders. Structurally distinct as a large family of mammalian proteins, neuraminidases (NEU1 through NEU4) possess dissimilar yet overlapping profiles of tissue expression, cellular/subcellular localization, and substrate specificity. NEU1 is well characterized for its lysosomal catabolic functions, with ubiquitous and abundant expression across such tissues as the kidney, pancreas, skeletal muscle, liver, lungs, placenta, and brain. NEU1 also exhibits a broad substrate range on the cell surface, where it plays hitherto underappreciated roles in modulating the structure and function of cellular receptors, providing a basis for it to be a potential drug target in various human diseases. This review seeks to summarize the recent progress in the research on NEU1-associated diseases and highlight the mechanistic implications of NEU1 in disease pathogenesis. An improved understanding of NEU1-associated diseases should help accelerate translational initiatives to develop novel or better therapeutics.

Dihalogenated nitrophenols in drinking water: Prevalence, resistance to household treatment, and cardiotoxic impact on zebrafish embryo

Dihalogenated nitrophenols (2,6-DHNPs), an emerging group of aromatic disinfection byproducts (DBPs) detected in drinking water, have limited available information regarding their persistence and toxicological risks. The present study found that 2,6-DHNPs are resistant to major drinking water treatment processes (sedimentation and filtration) and households methods (boiling, filtration, microwave irradiation, and ultrasonic cleaning). To further assess their health risks, we conducted a series of toxicology studies using zebrafish embryos as the model organism. Our findings reveal that these emerging 2,6-DHNPs showed lethal toxicity 248 times greater than that of the regulated DBP, dichloroacetic acid. Specifically, at sublethal concentrations, exposure to 2,6-DHNPs generated reactive oxygen species (ROS), caused apoptosis, inhibited cardiac looping, and induced cardiac failure in zebrafish. Remarkably, the use of a ROS scavenger, N-acetyl-l-cysteine, considerably mitigated these adverse effects, emphasizing the essential role of ROS in 2,6-DHNP-induced cardiotoxicity. Our findings highlight the cardiotoxic potential of 2,6-DHNPs in drinking water even at low concentrations of 19 μg/L and the beneficial effect of N-acetyl-l-cysteine in alleviating the 2,6-DHNP-induced cardiotoxicity. This study underscores the urgent need for increased scrutiny of these emerging compounds in public health discussions.

Chlorogenic Acid Attenuates Isoproterenol Hydrochloride-Induced Cardiac Hypertrophy in AC16 Cells by Inhibiting the Wnt/β-Catenin Signaling Pathway

Cardiac hypertrophy (CH) is an important characteristic in heart failure development. Chlorogenic acid (CGA), a crucial bioactive compound from honeysuckle, is reported to protect against CH. However, its underlying mechanism of action remains incompletely elucidated. Therefore, this study aimed to explore the mechanism underlying the protective effect of CGA on CH. This study established a CH model by stimulating AC16 cells with isoproterenol (Iso). The observed significant decrease in cell surface area, evaluated through fluorescence staining, along with the downregulation of CH-related markers, including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC) at both mRNA and protein levels, provide compelling evidence of the protective effect of CGA against isoproterenol-induced CH. Mechanistically, CGA induced the expression of glycogen synthase kinase 3β (GSK-3β) while concurrently attenuating the expression of the core protein β-catenin in the Wnt/β-catenin signaling pathway. Furthermore, the experiment utilized the Wnt signaling activator IM-12 to observe its ability to modulate the impact of CGA pretreatment on the development of CH. Using the Gene Expression Omnibus (GEO) database combined with online platforms and tools, this study identified Wnt-related genes influenced by CGA in hypertrophic cardiomyopathy (HCM) and further validated the correlation between CGA and the Wnt/β-catenin signaling pathway in CH. This result provides new insights into the molecular mechanisms underlying the protective effect of CGA against CH, indicating CGA as a promising candidate for the prevention and treatment of heart diseases.

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 μm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 μg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

Identification of Additives in Disposable Face Masks and Evaluation of Their Toxicity Using Marine Medaka (Oryzias melastigma)

The COVID-19 pandemic has resulted in huge amounts of face masks worldwide. However, there is a lack of awareness on the additives and their potential risk to aquatic ecosystems of face masks. To address this issue, the additives and their toxicity in 13 face masks (e.g., polypropylene, polyethylene, and polylactic acid) were determined using nontarget analysis and bioassays. A total of 826 organic additives including intermediates (14.8%), surfactants (9.3%), plasticizers (8.2%), and antioxidants (6.1%) were tentatively identified, with 213 compounds being assigned confidence levels of 1 and 2. Interestingly, polylactic acid masks contained more additives than most polypropylene or polyethylene masks. Among these additives, the concentration of tris(2-ethylhexyl) phosphate in masks was 9.4-978.2 ng/g with a 100% detection frequency. Furthermore, 13 metals such as zinc (up to 202.0 μg/g), copper (32.5 μg/g), and chromium (up to 5.7 μg/g) were detected in the face masks. The methanol extracts of the masks showed the developmental toxicity, swimming behavior, and/or endocrine disruption in embryos/larvae of Oryzias melastigma. The findings demonstrate that face masks contain various toxic additives to marine medaka, which deserves close attention to pollution by face masks.

Protective Roles and Therapeutic Effects of Gallic Acid in the Treatment of Cardiovascular Diseases: Current Trends and Future Directions

Cardiovascular diseases (CVDs) are serious life-threatening illnesses and significant problematic issues for public health having a heavy economic burden on all society worldwide. The high incidence of these diseases as well as high mortality rates make them the leading causes of death and disability. Therefore, finding novel and more effective therapeutic methods is urgently required. Gallic acid, an herbal medicine with numerous biological properties, has been utilized in the treatment of various diseases for thousands of years. It has been demonstrated that gallic acid possesses pharmacological potential in regulating several molecular and cellular processes such as apoptosis and autophagy. Moreover, gallic acid has been investigated in the treatment of CVDs both in vivo and in vitro. Herein, we aimed to review the available evidence on the therapeutic application of gallic acid for CVDs including myocardial ischemia-reperfusion injury and infarction, drug-induced cardiotoxicity, hypertension, cardiac fibrosis, and heart failure, with a focus on underlying mechanisms.

Sibjotang Protects against Cardiac Hypertrophy In Vitro and In Vivo

Cardiac hypertrophy is developed by various diseases such as myocardial infarction, valve diseases, hypertension, and aortic stenosis. Sibjotang (, Shizaotang, SJT), a classic formula in Korean traditional medicine, has been shown to modulate the equilibrium of body fluids and blood pressure. This research study sought to explore the impact and underlying process of Sibjotang on cardiotoxicity induced by DOX in H9c2 cells. In vitro, H9c2 cells were induced by DOX (1 μM) in the presence or absence of SJT (1-5 μg/mL) and incubated for 24 h. In vivo, SJT was administrated to isoproterenol (ISO)-induced cardiac hypertrophy mice (n = 8) at 100 mg/kg/day concentrations. Immunofluorescence staining revealed that SJT mitigated the enlargement of H9c2 cells caused by DOX in a dose-dependent way. Using SJT as a pretreatment notably suppressed the rise in cardiac hypertrophic marker levels induced by DOX. SJT inhibited the DOX-induced ERK1/2 and p38 MAPK signaling pathways. In addition, SJT significantly decreased the expression of the hypertrophy-associated transcription factor GATA binding factor 4 (GATA 4) induced by DOX. SJT also decreased hypertrophy-associated calcineurin and NFAT protein levels. Pretreatment with SJT significantly attenuated DOX-induced apoptosis-associated proteins such as Bax, caspase-3, and caspase-9 without affecting cell viability. In addition, the results of the in vivo study indicated that SJT significantly reduced the left ventricle/body weight ratio level. Administration of SJT reduced the expression of hypertrophy markers, such as ANP and BNP. These results suggest that SJT attenuates cardiac hypertrophy and heart failure induced by DOX or ISO through the inhibition of the calcineurin/NFAT/GATA4 pathway. Therefore, SJT may be a potential treatment for the prevention and treatment of cardiac hypertrophy that leads to heart failure.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we data-mined human and mouse heart ribosome profiling analyses and identified a double-stranded RNA (dsRNA) structure within the GATA4 uORF that cooperates with the start codon to augment uORF translation and inhibits mORF translation. A trans-acting RNA helicase DDX3X inhibits the GATA4 uORF-dsRNA activity and modulates the translational balance of uORF and mORF. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the broad utility of uORF-dsRNA- or mORF-targeting ASO to regulate mORF translation for other mRNAs. This work demonstrates that the uORF-dsRNA element regulates the translation of multiple mRNAs as a generalizable translational control mechanism. Moreover, we develop a valuable strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Loss of YTHDF2 Alters the Expression of m6A-Modified Myzap and Causes Adverse Cardiac Remodeling

How post-transcriptional regulation of gene expression, such as through N6-methyladenosine (m6A) messenger RNA methylation, impacts heart function is not well understood. We found that loss of the m6A binding protein YTHDF2 in cardiomyocytes of adult mice drove cardiac dysfunction. By proteomics, we found myocardial zonula adherens protein (MYZAP) within the top up-regulated proteins in knockout cardiomyocytes. We further demonstrated that YTHDF2 binds m6A-modified Myzap messenger RNA and controls its stability. Cardiac overexpression of MYZAP has been associated with cardiomyopathy. Thus, our findings provide an important new mechanism for the YTHDF2-dependent regulation of this target and therein its novel role in the maintenance of cardiac homeostasis.

Induction of Senescence by Loss of Gata4 in Cardiac Fibroblasts

Cardiac fibroblasts are a major source of cardiac fibrosis during heart repair processes in various heart diseases. Although it has been shown that cardiac fibroblasts become senescent in response to heart injury, it is unknown how the senescence of cardiac fibroblasts is regulated in vivo. Gata4, a cardiogenic transcription factor essential for heart development, is also expressed in cardiac fibroblasts. However, it remains elusive about the role of Gata4 in cardiac fibroblasts. To define the role of Gata4 in cardiac fibroblasts, we generated cardiac fibroblast-specific Gata4 knockout mice by cross-breeding Tcf21-MerCreMer mice with Gata4fl/fl mice. Using this mouse model, we could genetically ablate Gata4 in Tcf21 positive cardiac fibroblasts in an inducible manner upon tamoxifen administration. We found that cardiac fibroblast-specific deletion of Gata4 spontaneously induces senescence in cardiac fibroblasts in vivo and in vitro. We also found that Gata4 expression in both cardiomyocytes and non-myocytes significantly decreases in the aged heart. Interestingly, when αMHC-MerCreMer mice were bred with Gata4fl/fl mice to generate cardiomyocyte-specific Gata4 knockout mice, no senescent cells were detected in the hearts. Taken together, our results demonstrate that Gata4 deficiency in cardiac fibroblasts activates a program of cellular senescence, suggesting a novel molecular mechanism of cardiac fibroblast senescence.

Secondary structures that regulate mRNA translation provide insights for ASO-mediated modulation of cardiac hypertrophy

Translation of upstream open reading frames (uORFs) typically abrogates translation of main (m)ORFs. The molecular mechanism of uORF regulation in cells is not well understood. Here, we identified a double-stranded RNA (dsRNA) structure residing within the GATA4 uORF that augments uORF translation and inhibits mORF translation. Antisense oligonucleotides (ASOs) that disrupt this dsRNA structure promote mORF translation, while ASOs that base-pair immediately downstream (i.e., forming a bimolecular double-stranded region) of either the uORF or mORF start codon enhance uORF or mORF translation, respectively. Human cardiomyocytes and mice treated with a uORF-enhancing ASO showed reduced cardiac GATA4 protein levels and increased resistance to cardiomyocyte hypertrophy. We further show the general utility of uORF-dsRNA- or mORF- targeting ASO to regulate mORF translation for other mRNAs. Our work demonstrates a regulatory paradigm that controls translational efficiency and a useful strategy to alter protein expression and cellular phenotypes by targeting or generating dsRNA downstream of a uORF or mORF start codon.

Bullet points for discoveries

dsRNA within GATA4 uORF activates uORF translation and inhibits mORF translation. ASOs that target the dsRNA can either inhibit or enhance GATA4 mORF translation. ASOs can be used to impede hypertrophy in human cardiomyocytes and mouse hearts.uORF- and mORF-targeting ASOs can be used to control translation of multiple mRNAs.

Methamphetamine induces cardiomyopathy through GATA4/NF-κB/SASP axis-mediated cellular senescence

With the world pandemic of methamphetamine (METH), METH-associated cardiomyopathy (MAC) has become a widespread epidemic and is also recognized as a cause of heart failure in young people. The mechanism of occurrence and development of MAC is not clear. In this study, firstly, the animal model was evaluated by echocardiography and myocardial pathological staining. The results revealed that the animal model exhibited cardiac injury consistent with clinical alterations of MAC, and the mice developed cardiac hypertrophy and fibrosis remodeling, which led to systolic dysfunction and left ventricular ejection fraction (%LVEF) < 40%. The expression of cellular senescence marker proteins (p16 and p21) and senescence-associated secretory phenotype (SASP) was significantly increased in mouse myocardial tissue. Secondly, mRNA sequencing analysis of cardiac tissues revealed the key molecule GATA4, and Western blot, qPCR and immunofluorescence results showed that the expression level of GATA4 was significantly increased after METH exposure. Finally, knockdown of GATA4 expression in H9C2 cells in vitro significantly attenuated METH-induced cardiomyocyte senescence. Consequently, METH causes cardiomyopathy through cellular senescence mediated by the GATA4/NF-κB/SASP axis, which is a feasible target for the treatment of MAC.

DNA damage response and GATA4 signaling in cellular senescence and aging-related pathology

Aging is the continuous degradation of biological function and structure with time, and cellular senescence lies at its core. DNA damage response (DDR) can activate Ataxia telangiectasia-mutated serine/threonine kinase (ATM) and Rad3-related serine/threonine kinase (ATR), after which p53 activates p21, stopping the cell cycle and inducing cell senescence. GATA4 is a transcription factor that plays an important role in the development of many organs, such as the heart, testis, ovary, foregut, liver, and ventral pancreas. Studies have shown that GATA4 can also contribute to the DDR, leading to aging. Consistently, there is also evidence that the GATA4 signaling pathway is associated with aging-related diseases, including atherosclerosis and heart failure. This paper reviews the relationship between GATA4, DDR, and cellular senescence, as well as its effect on aging-related diseases.

A novel causative functional mutation in GATA6 gene is responsible for familial dilated cardiomyopathy as supported by in silico functional analysis

Dilated cardiomyopathy (DCM), one of the most common types of cardiomyopathies has a heterogeneous nature and can be seen in Mendelian forms. Next Generation Sequencing is a powerful tool for identifying novel variants in monogenic disorders. We used whole-exome sequencing (WES) and Sanger sequencing techniques to identify the causative mutation of DCM in an Iranian pedigree. We found a novel variant in the GATA6 gene, leading to substituting Histidine by Tyrosine at position 329, observed in all affected family members in the pedigree, whereas it was not established in any of the unaffected ones. We hypothesized that the H329Y mutation may be causative for the familial pattern of DCM in this family. The predicted models of GATA6 and H329Y showed the high quality according to PROCHECK and ERRAT. Nonetheless, simulation results revealed that the protein stability decreased after mutation, while the flexibility may have been increased. Hence, the mutation led to the increased compactness of GATA6. Overall, these data indicated that the mutation could affect the protein structure, which may be related to the functional impairment of GATA6 upon H329Y mutation, likewise their involvement in pathologies. Further functional investigations would help elucidating the exact mechanism.

Syringic acid mitigates isoproterenol-induced cardiac hypertrophy and fibrosis by downregulating Ereg

Gallic acid has been reported to mitigate cardiac hypertrophy, fibrosis and arterial hypertension. The effects of syringic acid, a derivative of gallic acid, on cardiac hypertrophy and fibrosis have not been previously investigated. This study aimed to examine the effects of syringic acid on isoproterenol‐treated mice and cells. Syringic acid mitigated the isoproterenol‐induced upregulation of heart weight to bodyweight ratio, pathological cardiac remodelling and fibrosis in mice. Picrosirius red staining, quantitative real‐time polymerase chain reaction (qRT‐PCR) and Western blotting analyses revealed that syringic acid markedly downregulated collagen accumulation and fibrosis‐related factors, including Fn1. The results of RNA sequencing analysis of Ereg expression were verified using qRT‐PCR. Syringic acid or transfection with si‐Ereg mitigated the isoproterenol‐induced upregulation of Ereg, Myc and Ngfr. Ereg knockdown mitigated the isoproterenol‐induced upregulation of Nppb and Fn1 and enhancement of cell size. Mechanistically, syringic acid alleviated cardiac hypertrophy and fibrosis by downregulating Ereg. These results suggest that syringic acid is a potential therapeutic agent for cardiac hypertrophy and fibrosis.

Towards Understanding the Gene-Specific Roles of GATA Factors in Heart Development: Does GATA4 Lead the Way?

Transcription factors play crucial roles in the regulation of heart induction, formation, growth and morphogenesis. Zinc finger GATA transcription factors are among the critical regulators of these processes. GATA4, 5 and 6 genes are expressed in a partially overlapping manner in developing hearts, and GATA4 and 6 continue their expression in adult cardiac myocytes. Using different experimental models, GATA4, 5 and 6 were shown to work together not only to ensure specification of cardiac cells but also during subsequent heart development. The complex involvement of these related gene family members in those processes is demonstrated through the redundancy among them and crossregulation of each other. Our recent identification at the genome-wide level of genes specifically regulated by each of the three family members and our earlier discovery that gata4 and gata6 function upstream, while gata5 functions downstream of noncanonical Wnt signalling during cardiac differentiation, clearly demonstrate the functional differences among the cardiogenic GATA factors. Such suspected functional differences are worth exploring more widely. It appears that in the past few years, significant advances have indeed been made in providing a deeper understanding of the mechanisms by which each of these molecules function during heart development. In this review, I will therefore discuss current evidence of the role of individual cardiogenic GATA factors in the process of heart development and emphasize the emerging central role of GATA4.

Secondary PVC microplastics are more toxic than primary PVC microplastics to Oryzias melastigma embryos

Irregular-shaped and partially degraded secondary microplastics (SMP) account for the majority of MPs in marine environments, yet little is known about their effects on marine organisms. In this study, we investigated the embryotoxicity of polyvinyl chloride SMP and primary microplastics (PMP) to the marine medaka Oryzias melastigma. This study aimed to determine the physical impacts of MPs and, for the first time, elucidate the underlying mechanisms of physical toxicity. SMP shortened hatching time and induced higher teratogenic effects on larvae relative to PMP, indicating a higher toxicity from SMP. Physical damage from SMP to the chorion surface appears to be the main toxicity mechanism, caused by their irregular shape and reduced aggregation relative to PMP. In contrast, real-time changes in oxygen demonstrated that hypoxia caused by greater PMP adsorption to the chorion surface contributes to the toxicological responses of this material relative to SMP. Modulation of genes involved in hypoxia-response, cardiac development and hatching confirmed the toxicity mechanisms of PMP and SMP. The chemical contribution to observed toxicity was negligible, confirming impacts derived from physical toxicity. Our findings highlight the negative effects of environmentally relevant SMP on the marine ecosystems.

Transcription Factors Involved in the Development and Prognosis of Cardiac Remodeling

To compensate increasing workload, heart must work harder with structural changes, indicated by increasing size and changing shape, causing cardiac remodeling. However, pathological and unlimited compensated cardiac remodeling will ultimately lead to decompensation and heart failure. In the past decade, numerous studies have explored many signaling pathways involved in cardiac remodeling, but the complete mechanism of cardiac remodeling is still unrecognized, which hinders effective treatment and drug development. As gene transcriptional regulators, transcription factors control multiple cellular activities and play a critical role in cardiac remodeling. This review summarizes the regulation of fetal gene reprogramming, energy metabolism, apoptosis, autophagy in cardiomyocytes and myofibroblast activation of cardiac fibroblasts by transcription factors, with an emphasis on their potential roles in the development and prognosis of cardiac remodeling.

Environmental relevant herbicide prometryn induces developmental toxicity in the early life stages of marine medaka (Oryzias melastigma) and its potential mechanism

Triazine herbicides have been widely detected in marine environments because of their extensive usage in agriculture, but their impact on marine organisms is unclear. In this study, marine medaka (Oryzias melastigma) embryos were exposed to 0, 1, 10, 100, and 1000 μg/L prometryn, one of the most detected triazine herbicides, to investigate its potential effects. The results showed that 1, 10, 100, and 1000 µg/L prometryn not only induced yolk sac shrinkage and heart malformations, but also significantly delayed the hatching time and increased the heart rate and hatching failure rate of embryos. Moreover, 1, 10, 100, and 1000 μg/L prometryn caused obvious malformations and decreased the body length of the newly hatched larvae. After 21 d of exposure, increased larval death rate, decreased body length and width, and higher lipid accumulation were observed in the larvae from all prometryn groups. Furthermore, prometryn exposure upregulated the expression levels of cardiac development-related genes GATA, COX, ATPase, SmyD1, EPO, FGF8, NKX2, and BMP4 in the larvae. Transcriptome analysis revealed that 10 μg/L prometryn upregulated 604 genes, and the topmost pathways of differentially expressed genes were the complement and coagulation cascades and AMPK signaling pathways. qPCR results confirmed that prometryn exposure significantly increased the expression levels of the complement and coagulation cascade genes f2, f5, c3, and c5. This study demonstrated that environmentally relevant concentrations of prometryn induced significant toxicity in the early life stages of marine medaka. Therefore, the health risks of herbicides to marine organisms are of great concern.

Integrative effects based on behavior, physiology and gene expression of tritiated water on zebrafish

Tritium is a water-soluble hydrogen isotope that releases beta rays during decay. In nature, tritium primarily exists as tritiated water (HTO), and its main source is nuclear power/processing plants. In recent decades, with the development of nuclear power industry, it is necessary to evaluate the impact of tritium on organisms. In this study, fertilized zebrafish embryos are treated with different HTO concentrations (3.7 × 10³ Bq/ml, 3.7 × 10⁴ Bq/ml, 3.7 × 10⁵ Bq/ml). After treatment with HTO, the zebrafish embryos developed without evident morphological changes. Nevertheless, the heart rate increased and locomotor activity decreased significantly. In addition, RNA-sequencing shows that HTO can affect gene expressions. The differentially expressed genes are enriched through many physiological processes and intracellular signaling pathways, including cardiac, cardiovascular, and nervous system development and the metabolism of xenobiotics by cytochrome P450. Moreover, the concentrations of thyroid hormones in the zebrafish decrease and the expression of thyroid hormone-related genes is disordered after HTO treatment. Our results suggest that exposure to HTO may affect the physiology and behaviors of zebrafish through physiological processes and intracellular signaling pathways and provide a theoretical basis for ecological risk assessment of tritium.

TFEB insufficiency promotes cardiac hypertrophy by blocking autophagic degradation of GATA4

Autophagosome-lysosome pathway (ALP) insufficiency has been suggested to play a critical role in the pathogenesis of cardiac hypertrophy. However, the mechanisms underlying ALP insufficiency remain largely unknown, and strategies to specifically manipulate ALP insufficiency for treating cardiac hypertrophy are lacking. Transcription factor EB (TFEB), as a master regulator of ALP, regulates the generation and function of autophagosomes and lysosomes. We found that TFEB was significantly decreased, whereas autophagosome markers were increased in phenylephrine (PE)-induced and transverse aortic constriction-induced cardiomyocyte hypertrophy and failing hearts from patients with dilated cardiomyopathy. Knocking down TFEB induced ALP insufficiency, as indicated by increased autophagosome markers, decreased light chain 3II flux, and cardiomyocyte hypertrophy manifested through increased levels of atrial natriuretic peptide and β-myosin heavy chain and enlarged cell size. The effects of TFEB knockdown were abolished by promoting autophagy. TFEB overexpression improved autophagic flux and attenuated PE-stimulated cardiomyocyte hypertrophy and transverse aortic constriction-induced hypertrophic remodeling, fibrosis, and cardiac dysfunction. Curcumin analog compound C1, a specific TFEB activator, similarly attenuated PE-induced ALP insufficiency and cardiomyocyte hypertrophy. TFEB knockdown increased the accumulation of GATA4, a transcription factor for several genes causing cardiac hypertrophy by blocking autophagic degradation of GATA4, whereas knocking down GATA4 attenuated TFEB downregulation-induced cardiomyocyte hypertrophy. Both TFEB overexpression and C1 promoted GATA4 autophagic degradation and alleviated PE-induced cardiomyocyte hypertrophy. In conclusion, TFEB downregulation plays a vital role in the development of pressure overload-induced cardiac hypertrophy by causing ALP insufficiency and blocking autophagic degradation. Activation of TFEB represents a potential therapeutic strategy for treating cardiac hypertrophy.

Pten Regulates Cardiomyocyte Differentiation by Modulating Non-CG Methylation via Dnmt3

The regulation of cardiomyocyte differentiation is a fundamental aspect of cardiac development and regenerative medicine. PTEN plays important roles during embryonic development. However, its role in cardiomyocyte differentiation remains unknown. In this study, a low-cost protocol for cardiomyocyte differentiation from mouse embryonic stem cells (ESCs) is presented and it is shown that Pten deletion potently suppresses cardiomyocyte differentiation. Transcriptome analysis shows that the expression of a series of cardiomyocyte marker genes is downregulated in Pten^-/- cardiomyocytes. Pten ablation induces Dnmt3b expression via the AKT/FoxO3a pathway and regulates the expression of a series of imprinted genes, including Igf2. Double knockout of Dnmt3l and Dnmt3b rescues the deficiency of cardiomyocyte differentiation of Pten^-/- ESCs. The DNA methylomes from wild-type and Pten^-/- embryoid bodies and cardiomyocytes are analyzed by whole-genome bisulfite sequencing. Pten deletion significantly promotes the non-CG (CHG and CHH) methylation levels of genomic DNA during cardiomyocyte differentiation, and the non-CG methylation levels of cardiomyocyte genes and Igf2 are increased in Pten^-/- cardiomyocytes. Igf2 or Igf1r deletion also suppresses cardiomyocyte differentiation through the MAPK/ERK signaling pathway, and IGF2 supplementation partially rescues the cardiomyocyte differentiation. Finally, Pten conditional knockout mice are generated and the role of PTEN in cardiomyocyte differentiation is verified in vivo.

Protocatechuic acid attenuates isoproterenol-induced cardiac hypertrophy via downregulation of ROCK1-Sp1-PKCγ axis

Cardiac hypertrophy is an adaptive response of the myocardium to pressure overload or adrenergic agonists. Here, we investigated the protective effects and the regulatory mechanism of protocatechuic acid, a phenolic compound, using a mouse model of isoproterenol-induced cardiac hypertrophy. Our results demonstrated that protocatechuic acid treatment significantly downregulated the expression of cardiac hypertrophic markers (Nppa, Nppb, and Myh7), cardiomyocyte size, heart weight to body weight ratio, cross-sectional area, and thickness of left ventricular septum and posterior wall. This treatment also reduced the expression of isoproterenol-induced ROCK1, Sp1, and PKCγ both in vivo and in vitro. To investigate the mechanism, we performed knockdown and overexpression experiments. The knockdown of ROCK1, Sp1, or PKCγ decreased the isoproterenol-induced cell area and the expression of hypertrophic markers, while the overexpression of Sp1 or PKCγ increased the levels of hypertrophic markers. Protocatechuic acid treatment reversed these effects. Interestingly, the overexpression of Sp1 increased cell area and induced PKCγ expression. Furthermore, experiments using transcription inhibitor actinomycin D showed that ROCK1 and Sp1 suppression by protocatechuic acid was not regulated at the transcriptional level. Our results indicate that protocatechuic acid acts via the ROCK1/Sp1/PKCγ axis and therefore has promising therapeutic potential as a treatment for cardiac hypertrophy.

New insights into the roles of glucocorticoid signaling dysregulation in pathological cardiac hypertrophy

Pathological cardiac hypertrophy is a process of abnormal remodeling of the myocardium in response to stress overload or ischemia that results in myocardial injury, which is an independent risk factor for the increased morbidity and mortality of heart failure. Elevated circulating glucocorticoids (GCs) levels are associated with an increased risk of pathological cardiac hypertrophy, but the exact role remains unclear. In the heart, GCs exerts physiological and pharmacological effects by binding the glucocorticoid receptor (GR, NR3C1). However, under the state of tissue damage or oxidative stress, GCs can also bind the closely related mineralocorticoid receptor (MR, NR3C2) to exert a detrimental effect on cardiac function. In addition, the bioavailability of GCs at the cellular level is mainly regulated by tissue-specific metabolic enzymes 11β-hydroxysteroid dehydrogenases (11β-HSDs), including 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and type 2 (11β-HSD2), which catalyze the interconversion of active GCs. In this paper, we provide an overview of GC signaling and its physiological roles in the heart and highlight the dynamic and diverse roles of GC signaling dysregulation, mediated by excessive ligand GCs levels, GR/MR deficiency or overexpression, and local GCs metabolic disorder by 11β-HSDs, in the pathology of cardiac hypertrophy. Our findings will provide new ideas and insights for the search for appropriate intervention targets for pathological cardiac hypertrophy.

Direct Reprogramming Induces Vascular Regeneration Post Muscle Ischemic Injury

Reprogramming non-cardiomyocytes (non-CMs) into cardiomyocyte (CM)-like cells is a promising strategy for cardiac regeneration in conditions such as ischemic heart disease. Here, we used a modified mRNA (modRNA) gene delivery platform to deliver a cocktail, termed 7G-modRNA, of four cardiac-reprogramming genes—Gata4 (G), Mef2c (M), Tbx5 (T), and Hand2 (H)—together with three reprogramming-helper genes—dominant-negative (DN)-TGFβ, DN-Wnt8a, and acid ceramidase (AC)—to induce CM-like cells. We showed that 7G-modRNA reprogrammed 57% of CM-like cells in vitro. Through a lineage-tracing model, we determined that delivering the 7G-modRNA cocktail at the time of myocardial infarction reprogrammed ∼25% of CM-like cells in the scar area and significantly improved cardiac function, scar size, long-term survival, and capillary density. Mechanistically, we determined that while 7G-modRNA cannot create de novo beating CMs in vitro or in vivo, it can significantly upregulate pro-angiogenic mesenchymal stromal cells markers and transcription factors. We also demonstrated that our 7G-modRNA cocktail leads to neovascularization in ischemic-limb injury, indicating CM-like cells importance in other organs besides the heart. modRNA is currently being used around the globe for vaccination against COVID-19, and this study proves this is a safe, highly efficient gene delivery approach with therapeutic potential to treat ischemic diseases.

Cardiomyocyte-specific Srsf3 deletion reveals a mitochondrial regulatory role

Serine-rich splicing factor 3 (SRSF3) was recently reported as being necessary to preserve RNA stability via an mTOR mechanism in a cardiac mouse model in adulthood. Here, we demonstrate the link between Srsf3 and mitochondrial integrity in an embryonic cardiomyocyte-specific Srsf3 conditional knockout (cKO) mouse model. Fifteen-day-old Srsf3 cKO mice showed dramatically reduced (below 50%) survival and reduced the left ventricular systolic performance, and histological analysis of these hearts revealed a significant increase in cardiomyocyte size, confirming the severe remodeling induced by Srsf3 deletion. RNA-seq analysis of the hearts of 5-day-old Srsf3 cKO mice revealed early changes in expression levels and alternative splicing of several transcripts related to mitochondrial integrity and oxidative phosphorylation. Likewise, the levels of several protein complexes of the electron transport chain decreased, and mitochondrial complex I-driven respiration of permeabilized cardiac muscle fibers from the left ventricle was impaired. Furthermore, transmission electron microscopy analysis showed disordered mitochondrial length and cristae structure. Together with its indispensable role in the physiological maintenance of mouse hearts, these results highlight the previously unrecognized function of Srsf3 in regulating the mitochondrial integrity.

Ambient air PM2.5 exposure induces heart injury and cardiac hypertrophy in rats through regulation of miR-208a/b, α/β-MHC, and GATA4

Ambient air fine particulate matter (PM2.5) may increase cardiovascular disease risks. In this study, we investigated the miR-208/GATA4/myosin heavy chain (MHC) regulation mechanisms on cardiac injury in rats after PM2.5 exposure via an animal inhalation device. The results showed that PM2.5 exposure for 2 months caused pathological heart injury, reduced nucleus-cytoplasm ratio, and increased the levels of CK-MB and cTnI, showing cardiac hypertrophy. Oxidative stress and inflammatory responses were also observed in rats' hearts exposed to PM2.5. Of note, PM2.5 exposure for 2-month significantly elevated GATA4 and β-MHC mRNA and protein expression compared with the corresponding controls, along with the high-expression of miR-208b. The ratios of β-MHC/α-MHC expression induced by PM2.5 were remarkably raised in comparison to their controls. It suggested that the up-regulation of miR-208b/β-MHC and GATA4 and the conversion from α-MHC to β-MHC may be the important causes of cardiac hypertrophy in rats incurred by PM2.5.

Neuraminidase 1 is a driver of experimental cardiac hypertrophy

AIMS 

Despite considerable therapeutic advances, there is still a dearth of evidence on the molecular determinants of cardiac hypertrophy that culminate in heart failure. Neuraminidases are a family of enzymes that catalyze the cleavage of terminal sialic acids from glycoproteins or glycolipids. This study sought to characterize the role of neuraminidases in pathological cardiac hypertrophy and identify pharmacological inhibitors targeting mammalian neuraminidases.

METHODS AND RESULTS 

Neuraminidase 1 (NEU1) was highly expressed in hypertrophic hearts of mice and rats, and this elevation was confirmed in patients with hypertrophic cardiomyopathy (n = 7) compared with healthy controls (n = 7). The increased NEU1 was mainly localized in cardiomyocytes by co-localization with cardiac troponin T. Cardiomyocyte-specific NEU1 deficiency alleviated hypertrophic phenotypes in response to transverse aortic constriction or isoproterenol hydrochloride infusion, while NEU1 overexpression exacerbated the development of cardiac hypertrophy. Mechanistically, co-immunoprecipitation coupled with mass spectrometry, chromatin immunoprecipitation, and luciferase assays demonstrated that NEU1 translocated into the nucleus and interacted with GATA4, leading to Foetal gene (Nppa and Nppb) expression. Virtual screening and experimental validation identified a novel compound C-09 from millions of compounds that showed favourable binding affinity to human NEU1 (KD = 0.38 μM) and effectively prevented the development of cardiac remodelling in cellular and animal models. Interestingly, anti-influenza drugs zanamivir and oseltamivir effectively inhibited mammalian NEU1 and showed new indications of cardio-protection.

CONCLUSIONS 

This work identifies NEU1 as a critical driver of cardiac hypertrophy and inhibition of NEU1 opens up an entirely new field of treatment for cardiovascular diseases.

Epitranscriptomics in the Heart: a Focus on m6A

PURPOSE OF REVIEW

Post-transcriptional modifications are key regulators of gene expression that allow the cell to respond to environmental stimuli. The most abundant internal mRNA modification is N6-methyladenosine (m⁶A), which has been shown to be involved in the regulation of RNA splicing, localization, translation, and decay. It has also been implicated in a wide range of diseases, and here, we review recent evidence of m⁶A's involvement in cardiac pathologies and processes.

RECENT FINDINGS

Studies have primarily relied on gain and loss of function models for the enzymes responsible for adding and removing the m⁶A modification. Results have revealed a multifaceted role for m⁶A in the heart's response to myocardial infarction, pressure overload, and ischemia/reperfusion injuries. Genome-wide analyses of mRNAs that are differentially methylated during cardiac stress have highlighted the importance of m⁶A in regulating the translation of specific categories of transcripts implicated in pathways such as calcium handling, cell growth, autophagy, and adrenergic signaling in cardiomyocytes. Regulation of gene expression by m⁶A is critical for cardiomyocyte homeostasis and stress responses, suggesting a key role for this modification in cardiac pathophysiology.

Systemic Bioinformatic Analyses of Nuclear-Encoded Mitochondrial Genes in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an autosomal dominant disease and mitochondria plays a key role in the progression in HCM. Here, we analyzed the expression pattern of nuclear-encoded mitochondrial genes (NMGenes) in HCM and found that the expression of NMGenes was significantly changed. A total of 316 differentially expressed NMGenes (DE-NMGenes) were identified. Pathway enrichment analyses showed that energy metabolism-related pathways such as "pyruvate metabolism" and "fatty acid degradation" were dysregulated, which highlighted the importance of energy metabolism in HCM. Next, we constructed a protein-protein interaction network based on 316 DE-NMGenes and identified thirteen hubs. Then, a total of 17 TFs (transcription factors) were predicted to potentially regulate the expression of 316 DE-NMGenes according to iRegulon, among which 8 TFs were already found involved in pathological hypertrophy. The remaining TFs (like GATA1, GATA5, and NFYA) were good candidates for further experimental verification. Finally, a mouse model of transverse aortic constriction (TAC) was established to validate the genes and results showed that DDIT4, TKT, CLIC1, DDOST, and SNCA were all upregulated in TAC mice. The present study represents the first effort to evaluate the global expression pattern of NMGenes in HCM and provides innovative insight into the molecular mechanism of HCM.

Cardiac Development: A Glimpse on Its Translational Contributions

Cardiac development is a complex developmental process that is initiated soon after gastrulation, as two sets of precardiac mesodermal precursors are symmetrically located and subsequently fused at the embryonic midline forming the cardiac straight tube. Thereafter, the cardiac straight tube invariably bends to the right, configuring the first sign of morphological left–right asymmetry and soon thereafter the atrial and ventricular chambers are formed, expanded and progressively septated. As a consequence of all these morphogenetic processes, the fetal heart acquired a four-chambered structure having distinct inlet and outlet connections and a specialized conduction system capable of directing the electrical impulse within the fully formed heart. Over the last decades, our understanding of the morphogenetic, cellular, and molecular pathways involved in cardiac development has exponentially grown. Multiples aspects of the initial discoveries during heart formation has served as guiding tools to understand the etiology of cardiac congenital anomalies and adult cardiac pathology, as well as to enlighten novels approaches to heal the damaged heart. In this review we provide an overview of the complex cellular and molecular pathways driving heart morphogenesis and how those discoveries have provided new roads into the genetic, clinical and therapeutic management of the diseased hearts.

Leech extract: A candidate cardioprotective against hypertension-induced cardiac hypertrophy and fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence of cardiovascular diseases (CVDs) has been increasing worldwide. Despite significant improvements in therapeutics and on-going developments of novel targeted-treatment regimens, cardiac diseases lack effective preventive and curative therapies with minimal side effects. Therefore, there is an urgent need to identify and propagate alternative and complementary therapies against cardiovascular diseases. Some traditional Chinese medicines can contribute to the prevention and treatment of CVDs and other chronic diseases, with few side effects. Hirudo, a medicinal leech, has been acclaimed for improving blood circulation and overcoming blood stagnation; however, the precise molecular mechanisms of leech extract treatment against pathological cardiac remodeling remain elusive. In this study, we aimed to delineate the molecular mechanisms of medicinal leech extract in the treatment of cardiac hypertrophy and fibrosis, using both in vitro and in vivo assessments.

MATERIALS AND METHODS

We conducted in vitro and in vivo animal experiments, including cell-viability assays, fluorescence microscopy, immunoblotting, immunohistochemistry, and Masson's trichrome staining.

RESULTS

Pre-treatment with leech extract conferred a survival benefit to spontaneously-hypertensive rats (SHRs) and significantly reduced angiotensin II (ANG II)-induced cardiac hypertrophy and fibrosis. ANG II-stimulated cardiac hypertrophy markers were attenuated by leech extract treatment, versus controls. Translational expression of stress-associated mitogen-activated protein kinases (MAPKs) was also repressed. In vivo, leech extract treatment significantly ameliorated the cardiac hypertrophy phenotype in SHRs and diminished interstitial fibrosis, accompanied with reduced fibrosis markers.

CONCLUSION

Leech extract treatment under a hypertensive condition exerted significant cardio-protective benefits by reducing the expression of cardiac hypertrophy-related transcription factors, stress-associated MAPKs, and fibrosis mediators. Our findings imply that medicinal leach extract may be effective against hypertension-induced cardiac hypertrophy and fibrosis.

Deficit of glucocorticoid-induced leucine zipper amplifies angiotensin-induced cardiomyocyte hypertrophy and diastolic dysfunction

Poor prognosis in heart failure and the lack of real breakthrough strategies validate targeting myocardial remodelling and the intracellular signalling involved in this process. So far, there are no effective strategies to counteract hypertrophy, an independent predictor of heart failure progression and death. Glucocorticoid-induced leucine zipper (GILZ) is involved in inflammatory signalling, but its role in cardiac biology is unknown. Using GILZ-knockout (KO) mice and an experimental model of hypertrophy and diastolic dysfunction, we addressed the role of GILZ in adverse myocardial remodelling. Infusion of angiotensin II (Ang II) resulted in myocardial dysfunction, inflammation, apoptosis, fibrosis, capillary rarefaction and hypertrophy. Interestingly, GILZ-KO showed more evident diastolic dysfunction and aggravated hypertrophic response compared with WT after Ang II administration. Both cardiomyocyte and left ventricular hypertrophy were more pronounced in GILZ-KO mice. On the other hand, Ang II-induced inflammatory and fibrotic phenomena, cell death and reduction in microvascular density, remained invariant between the WT and KO groups. The analysis of regulators of hypertrophic response, GATA4 and FoxP3, demonstrated an up-regulation in WT mice infused with Ang II; conversely, such an increase did not occur in GILZ-KO hearts. These data on myocardial response to Ang II in mice lacking GILZ indicate that this protein is a new element that can be mechanistically involved in cardiovascular pathology.

Remodeling of the m6A landscape in the heart reveals few conserved post-transcriptional events underlying cardiomyocyte hypertrophy

Regulation of gene expression plays a fundamental role in cardiac stress-responses. Modification of coding transcripts by adenosine methylation (m⁶A) has recently emerged as a critical post-transcriptional mechanism underlying heart disease. Thousands of mammalian mRNAs are known to be m⁶A-modified, suggesting that remodeling of the m⁶A landscape may play an important role in cardiac pathophysiology. Here we found an increase in m⁶A content in human heart failure samples. We then adopted genome-wide analysis to define all m⁶A-regulated sites in human failing compared to non-failing hearts and identified targeted transcripts involved in histone modification as enriched in heart failure. Further, we compared all m⁶A sites regulated in human hearts with the ones occurring in isolated rat hypertrophic cardiomyocytes to define cardiomyocyte-specific m⁶A events conserved across species. Our results identified 38 shared transcripts targeted by m⁶A during stress conditions, and 11 events that are unique to unstressed cardiomyocytes. Of these, further evaluation of select mRNA and protein abundances demonstrates the potential impact of m⁶A on post-transcriptional regulation of gene expression in the heart.

Hematopoietic Stem Cell Transcription Factors in Cardiovascular Pathology

Transcription factors as multifaceted modulators of gene expression that play a central role in cell proliferation, differentiation, lineage commitment, and disease progression. They interact among themselves and create complex spatiotemporal gene regulatory networks that modulate hematopoiesis, cardiogenesis, and conditional differentiation of hematopoietic stem cells into cells of cardiovascular lineage. Additionally, bone marrow-derived stem cells potentially contribute to the cardiovascular cell population and have shown potential as a therapeutic approach to treat cardiovascular diseases. However, the underlying regulatory mechanisms are currently debatable. This review focuses on some key transcription factors and associated epigenetic modifications that modulate the maintenance and differentiation of hematopoietic stem cells and cardiac progenitor cells. In addition to this, we aim to summarize different potential clinical therapeutic approaches in cardiac regeneration therapy and recent discoveries in stem cell-based transplantation.

Effects of PM2.5 exposure in utero on heart injury, histone acetylation and GATA4 expression in offspring mice

Atmospheric fine particulate matter exposure (PM_2.5) can increase the incidence and mortality of heart disease, and raise the risk of fetal congenital heart defect, which have recently drawn much attention. In this study, C57BL/6 mice were exposed to PM_2.5 (approximately equivalent to 174 μg/m³) by intratracheal instillation during the gestation. After birth, 10 weeks old offspring mice were divided into four groups: male exposed group (ME), female exposed group (FE), male control group (MC), female control group (FC). The pathological injury, pro-inflammatory cytokines, histone acetylation levels, and expressions of GATA-binding protein 4 (GATA4) and downstream genes were investigated. The results showed that exposure to PM_2.5 in utero increased pathological damage and TNF-α and IL-6 levels in hearts of offspring mice, and effects in ME were more serious than FE. Notably, GATA4 protein levels in hearts in ME were significantly lower than that of MC, accompanied by down-regulation of histone acetyltransferase (HAT)-p300 and up-regulation of histone deacetylase-SIRT3. As GATA4 downstream genes, ratios of β-MHC gene expression to α-MHC significantly raised in ME relative to the MC. Results of chromatin immunoprecipitation (ChIP)-qPCR assay found that binding levels of acetylated histone 3 lysine 9 (H3K9ac) in GATA4 promoter region in the hearts of ME or FE were markedly decreased compared with their corresponding control groups. It suggested that maternal exposure to PM_2.5 may cause cardiac injury in the offspring, heart damage of male mice was worse than female mice, in which process HAT-p300, H3K9ac, transcription factor GATA4 may play an important regulation role.

Crosstalk between cardiomyocytes and noncardiomyocytes is essential to prevent cardiomyocyte apoptosis induced by proteasome inhibition

Heart is a multi-cellular organ made up of various cell types interacting with each other. Cardiomyocytes may benefit or suffer from crosstalk with noncardiomyocytes in response to diverse kinds of cardiac stresses. Proteasome dysfunction is a common cardiac stress which causes cardiac proteotoxicity and contributes to cardiac diseases such as heart failure and myocardial infarction. The role of crosstalk between cardiomyocytes and noncardiomyocytes in defense of cardiac proteotoxicity remains unknown. Here, we report a cardiomyocyte-specific survival upon proteasome inhibition in a heterogeneous culture consisting of cardiomyocytes and other three major cardiac cell types. Conversely, cardiomyocyte apoptosis is remarkably induced by proteasome inhibition in a homogeneous culture consisting of a majority of cardiomyocytes, demonstrating an indispensable role of noncardiomyocytes in the prevention of cardiomyocyte apoptosis resulting from proteasome inhibition. We further show that cardiomyocytes express brain natriuretic peptide (BNP) as an extracellular molecule in response to proteasome inhibition. Blockade of BNP receptor on noncardiomyocytes significantly exacerbated the cardiomyocyte apoptosis, indicating a paracrine function of cardiomyocyte-released extracellular BNP in activation of a protective feedback from noncardiomyocytes. Finally, we demonstrate that proteasome inhibition-activated transcriptional up-regulation of BNP in cardiomyocytes was associated with the dissociation of repressor element 1 silencing transcription factor (REST)/ histone deacetylase 1 (HDAC1) repressor complex from BNP gene promoter. Consistently, the induction of BNP could be further augmented by the treatment of HDAC inhibitors. We conclude that the crosstalk between cardiomyocytes and noncardiomyocytes plays a crucial role in the protection of cardiomyocytes from proteotoxicity stress, and identify cardiomyocyte-released BNP as a novel paracrine signaling molecule mediating this crosstalk. These findings provide new insights into the key regulators and cardioprotective mechanism in proteasome dysfunction-related cardiac diseases.

Deacetylase-independent function of SIRT6 couples GATA4 transcription factor and epigenetic activation against cardiomyocyte apoptosis

SIRT6 deacetylase activity improves stress resistance via gene silencing and genome maintenance. Here, we reveal a deacetylase-independent function of SIRT6, which promotes anti-apoptotic gene expression via the transcription factor GATA4. SIRT6 recruits TIP60 acetyltransferase to acetylate GATA4 at K328/330, thus enhancing its chromatin binding capacity. In turn, GATA4 inhibits the deacetylase activity of SIRT6, thus ensuring the local chromatin accessibility via TIP60-promoted H3K9 acetylation. Significantly, the treatment of doxorubicin (DOX), an anti-cancer chemotherapeutic, impairs the SIRT6-TIP60-GATA4 trimeric complex, blocking GATA4 acetylation and causing cardiomyocyte apoptosis. While GATA4 hyperacetylation-mimic retains the protective effect against DOX, the hypoacetylation-mimic loses such ability. Thus, the data reveal a novel SIRT6-TIP60-GATA4 axis, which promotes the anti-apoptotic pathway to prevent DOX toxicity. Targeting the trimeric complex constitutes a new strategy to improve the safety of DOX chemotherapy in clinical application.

Inhibition of the ROS-EGFR Pathway Mediates the Protective Action of Nox1/4 Inhibitor GKT137831 against Hypertensive Cardiac Hypertrophy via Suppressing Cardiac Inflammation and Activation of Akt and ERK1/2

Oxidative stress, inflammation, and hypertension constitute a self-perpetuating vicious circle to exacerbate hypertension and subsequent hypertensive cardiac hypertrophy. NADPH oxidase (Nox) 1/4 inhibitor GKT137831 alleviates hypertensive cardiac hypertrophy in models of secondary hypertension; however, it remains unclear about its effect on hypertensive cardiac hypertrophy in models of essential hypertension. This study is aimed at determining the beneficial role of GKT137831 in hypertensive cardiac hypertrophy in spontaneously hypertensive rats (SHRs) and its mechanisms of action. Treating with GKT137831 prevented cardiac hypertrophy in SHRs. Likewise, decreasing production of reactive oxygen species (ROS) with GKT137831 reduced epidermal growth factor receptor (EGFR) activity in the left ventricle of SHRs. Additionally, EGFR inhibition also reduced ROS production in the left ventricle and blunted hypertensive cardiac hypertrophy in SHRs. Moreover, inhibition of the ROS-EGFR pathway with Nox1/4 inhibitor GKT137831 or selective EGFR inhibitor AG1478 reduced protein and mRNA levels of proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β), as well as the activities of Akt and extracellular signal-regulated kinase (ERK) 1/2 in the left ventricle of SHRs. In summary, GKT137831 prevents hypertensive cardiac hypertrophy in SHRs, Nox-deprived ROS regulated EGFR activation through positive feedback in the hypertrophic myocardium, and inhibition of the ROS-EGFR pathway mediates the protective role of GKT137831 in hypertensive cardiac hypertrophy via repressing cardiac inflammation and activation of Akt and ERK1/2. This research will provide additional details for GKT137831 to prevent hypertensive cardiac hypertrophy.

Magnesium Deficiency Causes Transcriptional Downregulation of Kir2.1 and Kv4.2 Channels in Cardiomyocytes Resulting in QT Interval Prolongation

BACKGROUND

Mechanisms for QT interval prolongation and cardiac arrhythmogenesis in hypomagnesemia are poorly understood. This study investigated the potential molecular mechanism for QT prolongation caused by magnesium (Mg) deficiency in rats by using the patch clamp technique and molecular biology.

METHODS AND RESULTS

Male Wistar rats were fed an Mg-free diet or a normal diet for up to 12 weeks. There was QT prolongation in the ECG of Mg-deficient rats, and cardiomyocytes from these rats showed prolongation of action potential duration. Electrophysiological studies showed that inward-rectifying K+current (IK1) and transient outward K+current (Ito) were decreased in Mg-deficient cardiomyocytes, and these findings were consistent with the downregulation of mRNA, as well as protein levels of Kir2.1 and Kv4.2. In Mg-deficient cardiomyocytes, transcription factors, GATA4 and NFAT, were upregulated, whereas CREB was downregulated. In contrast to Mg deficiency, cellular Mg2+overload in cultured cardiomyocytes resulted in the upregulation of Kir2.1 and Kv4.2, which was accompanied by the downregulation of GATA4 and NFATc4, and the upregulation of CREB. Activation of NFAT and inhibition of CREB reduced Kv4.2-Ito, whereas Kir2.1-IK1was reduced by CREB inhibition but not by NFTA activation.

CONCLUSIONS

Intracellular Mg deficiency downregulates IK1and Itoin cardiomyocytes, and this is mediated by the transcription factors, NFAT and CREB. These results provide a novel mechanism for the long-term QT interval prolongation in hypomagnesemia.

Silencing of long non-coding RNA SOX21-AS1 inhibits lung adenocarcinoma invasion and migration by impairing TSPAN8 via transcription factor GATA6

Here, we revealed the novel role of long non-coding RNAs (lncRNAs) SOX21 antisense RNA 1 (SOX21-AS1)/TSPAN8/GATA6 in progression of lung adenocarcinoma. SOX21-AS1 expression was quantified in lung adenocarcinoma tissues and cells by RT-qPCR. Then, gain- and loss-of-function experiments were conducted in lung adenocarcinoma cells. Expression of GATA6, TSPAN8 and extracellular signal-regulated kinase (ERK) signaling pathway-related genes was determined in lung adenocarcinoma cells by western blot analysis. The interaction and relationship among SOX21-AS1, GATA6 and TSPAN8 were predicted and verified respectively by RNA pull down, RIP, ChIP, and dual-luciferase reporter assays. Next, lung adenocarcinoma cell proliferation, colony formation, invasion and migration were assessed by 5-ethynyl-2'-deoxyuridine staining, colony formation assay and Transwell assay. Xenograft tumors were established in nude mice and the tumor growth was observed and recorded. SOX21-AS1 was observed to be highly expressed in lung adenocarcinoma tissues. The overexpression of SOX21-AS1, GATA6 or TSPAN8 obviously enhanced cell biological functions in lung adenocarcinoma. Meanwhile, SOX21-AS1 interacted with GATA6 which bound to TSPAN8 promoter and promoted TSPAN8 expression, which further enhanced cell colony formation, proliferation and invasion, and also activated ERK signaling pathway. Silencing of SOX21-AS1 and inhibiting its binding to GATA6 downregulate TSPAN8 and thereby exert anti-oncogenic effects in lung adenocarcinoma.