SIRT2 Acts as a Cardioprotective Deacetylase in Pathological Cardiac Hypertrophy

Thymic Bmi-1 hampers γδT17 generation and its derived RORγt-IL-17A signaling to delay cardiac aging

New immunosenescence targets for preventing senescence-associated pathological cardiac hypertrophy (SA-PCH) need to be explored. In the present study, with physiologically aged human and mouse samples, the IL-17A level increased with physiological aging, heart failure (HF), and SA-PCH and was negatively correlated with thymic Bmi-1 expression. Bmi-1f/fLckCre+ mice and Bmi-1f/f littermates were generated to determine whether Bmi-1 delayed T cell aging by maintaining thymic T cell development to prevent SA-PCH. As a result, Bmi-1 promoted thymic T cell development by upregulating Notch signaling and prevented DN1 T cells from differentiating into γδT17 cells by downregulating γδT17 cell differentiation signaling. Bmi-1 upregulated Notch signaling by inhibiting p53-mediated Ikzf1 transcription at the -1,863 to -1,849 Ikzf1 promoter region. Bmi-1-RING1B promoted RORγt ubiquitination and degradation by proteasome to inhibit the production of IL-17A in γδT17 cells. Bmi-1 also downregulated Rorc transcribed by c-Maf by trimethylating H3K27 at the -1,511 to -1,497 Rorc promoter region. Subsequently, the number of peripheral γδT17 cells infiltrating the heart tissues was reduced, while alleviating IL-17A-dependent cardiac aging, hypertrophy, dysfunction, senescence-associated secretory phenotype (SASP), and macrophage-myofibroblast transition, ultimately improving SA-PCH. The RORγt inhibitor SR1001 and IL-17A neutralizing antibody ixekizumab prevented thymic RORγt-IL-17A-dependent SA-PCH. Furthermore, RORγt bound to Bmi-1 through ARG237 and to RING1B through GLU235, which could be used as a therapeutic strategy for SA-PCH to construct binding peptides promoting Bmi-1-RING1B binding to RORγt and degrading RORγt for inhibiting γδT17 cell differentiation and IL-17A production. Thus, thymic Bmi-1 prevented IL-17A-dependent SA-PCH by decreasing γδT17 cell numbers.

Microbiota-derived indole acetic acid extends lifespan through the AhR-Sirt2 pathway in Drosophila

Disruption of aryl hydrocarbon receptor (AhR) signaling and aberrant tryptophan metabolism have been shown to be highly associated with aging and age-related disorders. However, the underlying molecular mechanisms by which the AhR-mediated signaling pathway contributes to the aging process remain largely unknown. In this study, we find that aged Drosophila exhibits markedly reduced tryptophan metabolism leading to impaired AhR ligands, especially indole acetic acid (IAA), compared with their young controls. Supplementation with IAA, produced from Lactobacillus spp., dose-dependently extends the lifespan of Drosophila and improves healthy aging with resistance to starvation and oxidative stress. Mechanistically, activation of AhR by IAA markedly enhances Sirt2 activity by binding to its promoter, thereby inhibiting downstream TOR signaling and related fatty acid and amino acid metabolism. Both Ahr and Sirt2 mutant flies with IAA supplementation display a negligible lifespan extension, suggesting that AhR-mediated Sirt2 signaling contributes to lifespan extension in flies upon IAA supplementation. From the perspective of host metabolism, IAA supplementation significantly increases unsaturated fatty acids (UFAs) in aged flies, which are regarded to be beneficial for healthy status. These findings provide new insights into the physiological functions of AhR involved in the aging process by mediating Sirt2 signaling.

IMPORTANCE

Disruption of aryl hydrocarbon receptor (AhR) signaling and aberrant tryptophan metabolism contribute to aging and age-related disorders, but the underlying molecular mechanisms are largely unknown. Using multiomics analyses combined with biochemical assays, this study reveals that AhR activation by indole acetic acid (IAA) effectively extends the lifespan accompanied by improved healthy aging in Drosophila via the AhR-Sirt2 pathway.

Emerging Epigenetic Therapies for the Treatment of Cardiac Fibrosis

Fibrosis is a pathological process characterized by excessive extracellular matrix (ECM) deposition, leading to tissue stiffening and organ dysfunction. It is a major contributor to chronic diseases affecting various organs, with limited therapeutic options available. Among the different forms of fibrosis, cardiac fibrosis is particularly relevant due to its impact on cardiovascular diseases (CVDs), which remain the leading cause of morbidity and mortality worldwide. This process is driven by activated cardiac fibroblasts (CFs), which promote ECM accumulation in response to chronic stressors. Epigenetic mechanisms, including DNA methylation, histone modifications, and chromatin remodeling, are key regulators of fibroblast activation and fibrotic gene expression. Enzymes such as DNA methyltransferases (DNMTs), histone methyltransferases (HMTs), histone acetyltransferases (HATs), and histone deacetylases (HDACs) have emerged as potential therapeutic targets, and epigenetic inhibitors have shown promise in modulating these enzymes to attenuate fibrosis by controlling fibroblast function and ECM deposition. These small-molecule compounds offer advantages such as reversibility and precise temporal control, making them attractive candidates for therapeutic intervention. This review aims to provide a comprehensive overview of the mechanisms by which epigenetic regulators influence cardiac fibrosis and examines the latest advances in preclinical epigenetic therapies. By integrating recent data from functional studies, single-cell profiling, and drug development, it highlights key molecular targets, emerging therapeutic strategies, and current limitations, offering a critical framework to guide future research and clinical translation.

Natural Bioproducts with Epigenetic Properties for Treating Cardiovascular Disorders

Cardiovascular disorders (CVDs) are the leading cause of mortality worldwide, highlighting an urgent need for innovative therapeutic strategies. Recent advancements highlight the potential of naturally derived bioproducts with epigenetic properties to offer protection against CVDs. These compounds act on key epigenetic mechanisms, DNA methylation, histone modifications, and non-coding RNA regulation to modulate gene expression essential for cardiovascular health. This review explores the effects of various bioproducts, such as polyphenols, flavonoids, and other natural extracts, on these epigenetic modifications and their potential benefits in preventing and managing CVDs. We discuss recent discoveries and clinical applications, providing insights into the epigenetic regulatory mechanisms of these compounds as potential epidrugs, naturally derived agents with promising therapeutic prospects in epigenetic therapy for CVDs.

Metformin activates SIRT2 to improve insulin resistance and promote granulosa cell glycolysis in a rat model of polycystic ovary syndrome

RESEARCH QUESTION

What is the mechanism by which metformin enhances insulin sensitivity, improves granulosa cell glycolysis and induces ovulation in a rat model of polycystic ovary syndrome (PCOS)?

DESIGN

Analysis of the GSE168404 gene expression profile in the Gene Expression Omnibus database revealed increased levels of IGF1 and decreased levels of glycolytic enzymes (HK2, LDHA, PKM2) in the granulosa cells of PCOS patients. To explore the effects of metformin on the imbalance in glycolysis induced by insulin resistance (IR), experiments were conducted using Sprague-Dawley rats and KGN cells (human ovarian granulosa cells). Oestrous cycles were monitored in control, PCOS model (induced by letrozole and a high-fat diet) and metformin-treated PCOS groups. Analyses of body weight, hormone concentrations and biochemical, histopathological, immunohistochemical and glycolytic pathways were performed. KGN cells were used to model insulin resistance with insulin, and AGK2 was used specifically to inhibit sirtuin 2 (SIRT2), while metformin was applied.

RESULTS

Metformin significantly improved insulin resistance in PCOS rats, reduced insulin-like growth factor 1 (IGF1) protein and mRNA expression (all P ≤ 0.0348) and increased IGF1 receptor (IGF1R) impression (all P ≤ 0.0361). Insulin inhibited glycolytic activity in KGN cells, but metformin attenuated this effect (all P ≤ 0.0255). Metformin reversed the inhibition of SIRT2 in PCOS rat ovaries (all P ≤ 0.0483) and restored glycolysis in KGN cells treated by AGK2 (all P ≤ 0.0369).

CONCLUSION

Metformin enhances insulin sensitivity and restores glycolysis by regulating SIRT2, which may improve follicular development and reduce ovarian damage in PCOS rats, offering a potential clinical treatment strategy for PCOS.

Acetylation and deacetylation dynamics in stress response to cancer and infections

In response to stress stimuli, cells have evolved various mechanisms to integrate internal and external signals to achieve dynamic homeostasis. Lysine acetyltransferase (KATs) and deacetyltransferase (KDACs) are the key modulators of epigenetic modifications, enabling cells to modulate cellular responses through the acetylation and deacetylation of both histone and nonhistone proteins. Understanding the signaling pathways involved in cellular stress response, along with the roles of KATs and KDACs may pave the way for the development of novel therapeutic strategies. This review discusses the molecular mechanisms of acetylation and deacetylation in stress responses related to tumorigenesis, viral and bacterial infections. In tumorigenesis section, we focused on the tumor cells' intrinsic and external molecules and signaling pathways regulated by acetylation and deacetylation modification. In viral and bacterial infections, we summarized the update research on acetylation and deacetylation modification in viral and bacterial infections, which systematical introduction on this topic is not too much. Additionally, we provide an overview of current therapeutic interventions and clinical trials involving KAT and KDAC inhibitors in the treatment of cancer, as well as viral and bacterial infection-related diseases.

Sirt2 deficiency aggravates intramuscular adipose tissue infiltration and impairs myogenesis with aging in male mice

Sarcopenia, closely associated with other diseases such as diabetes, metabolic syndrome, and osteoporosis, significantly impacts aging populations. It is characterized by muscle atrophy, increased intramuscular adipose tissue, impaired myogenesis, chronic low-grade inflammation, and reduced muscle function. The mechanisms behind aging muscle remain incompletely understood. This study aims to elucidate the role of Sirt2 in the aging process of skeletal muscles and enhance our understanding of the underlying mechanisms. Sirt2 expression was reduced in aging muscle of male mice by 40%, compared to young muscle. Aged male Sirt2 knockout mice exhibit increased intramuscular adipose tissue infiltration by 8.5-fold changes. Furthermore, the deletion of Sirt2 exacerbated myogenesis impairment in aged muscle by decreasing the expression of Pax7 (50%) and NogoA (80%), compared to age- and sex- matched counterparts, emphasizing the role of Sirt2 in pathology of aging muscle. Additionally, long-term Sirt2 deletion affected other Sirtuin subfamily members, with decreased expressions of Sirt1 (65%), Sirt4 (94%), and Sirt5 (71%), and increased expressions of Sirt6 (4.6-fold) and Sirt7 (2.8-fold) in old male Sirt2 knockout mice, while there was no difference of these gene expression in young male mice. This study underscores the critical need for a deeper investigation into Sirt2, promising new insights that could lead to targeted therapies for sarcopenia, ultimately improving the quality of life in the elderly.

SIRT2 inhibition attenuates myofibroblast transition through autophagy-mediated ciliogenesis in renal epithelial cells

Myofibroblast transition plays a crucial role in both fibrotic diseases and wound healing. Although SIRT2 regulates fibrosis, its mechanisms of action remain poorly understood. This study aimed to investigate the effects of SIRT2 inhibition on myofibroblast transition in human renal cells under quiescent conditions. HK-2 kidney proximal tubular epithelial cells were starved of serum, resulting in the formation of primary cilia. Transforming growth factor-β (TGF-β) stimulation reduced both the number of ciliated cells and ciliary length. The ciliary defects resulted from a failure in autophagy termination, leading to the accumulation of OFD1, a negative regulator of ciliogenesis, at centriolar satellites. This phenomenon was correlated with the upregulation of fibrosis-related proteins. To elucidate the role of SIRT2 in the autophagy-ciliogenesis-fibrosis axis, cells were treated with AGK2, a specific inhibitor of SIRT2. AGK2 treatment promoted the formation of both autophagosomes and autolysosomes and facilitated OFD1 degradation at the centriolar satellites, resulting in the lengthening of primary cilia. Restoration of primary cilia by AGK2 was associated with the suppression of myofibroblast transition. In conclusion, SIRT2 inhibition attenuates TGF-β-induced fibrosis by promoting autophagy-mediated ciliogenesis. This study highlights SIRT2 as a potential therapeutic target for fibrotic diseases.

Cardiomyocyte PRL2 Promotes Cardiac Hypertrophy via Directly Dephosphorylating AMPKα2

BACKGROUND

Pathological cardiac hypertrophy can result in heart failure. Protein dephosphorylation plays a primary role in the mediation of various cellular processes in cardiomyocytes. Here, we investigated the effects of a protein tyrosine phosphatase, PRL2 (phosphatase of regenerative liver 2), on pathological cardiac hypertrophy.

METHODS

The PRL2 knockout mice were subjected to angiotensin II infusion or transverse aortic constriction to induce myocardial hypertrophy and cardiac dysfunction. RNA-sequencing analysis was performed to explore the underlying mechanisms. Mass spectrometry and bio-layer interferometry assays were used to identify AMPKα2 (AMP-activated protein kinase α2) as an interacting protein of PRL2. Mutant plasmids of AMPKα2 were used to clarify how PRL2 interacts and dephosphorylates AMPKα2.

RESULTS

A significant upregulation of PRL2 was observed in hypertrophic myocardium tissues in mice and patients with heart failure. PRL2 deficiency alleviated cardiac hypertrophy, fibrosis, and dysfunction in mice challenged with angiotensin II infusion or transverse aortic constriction. Transcriptomic and biochemical analyses showed that PRL2 knockout or silence maintained AMPKT172 phosphorylation and subsequent mitochondrial integrity in angiotensin II-challenged heart tissues or cardiomyocytes. Mass spectrometry-based interactome assay indicated AMPKα2 subunit as the substrate of PRL2. Mechanistically, PRL2 binds to the C-terminal domain of AMPKα2 and then dephosphorylates AMPKα2T172 via its active site C46. Adeno-associated virus 9-mediated deficiency of cardiomyocyte PRL2 also protected cardiac mitochondrial function and showed cardioprotective effects in angiotensin II-challenged mice, but these benefits were not observed in AMPKα2-/- mice.

CONCLUSIONS

This study reveals that PRL2, as a novel AMPK-regulating phosphatase, promotes mitochondrial instability and hypertrophic injury in cardiomyocytes and provides PLR2 as a potential target for future drug development treating heart failure.

Activation and inhibition of sirtuins: From bench to bedside

The sirtuin family comprises seven NAD+-dependent enzymes which catalyze protein lysine deacylation and mono ADP-ribosylation. Sirtuins act as central regulators of genomic stability and gene expression and control key processes, including energetic metabolism, cell cycle, differentiation, apoptosis, and aging. As a result, all sirtuins play critical roles in cellular homeostasis and organism wellness, and their dysregulation has been linked to metabolic, cardiovascular, and neurological diseases. Furthermore, sirtuins have shown dichotomous roles in cancer, acting as context-dependent tumor suppressors or promoters. Given their central role in different cellular processes, sirtuins have attracted increasing research interest aimed at developing both activators and inhibitors. Indeed, sirtuin modulation may have therapeutic effects in many age-related diseases, including diabetes, cardiovascular and neurodegenerative disorders, and cancer. Moreover, isoform selective modulators may increase our knowledge of sirtuin biology and aid to develop better therapies. Through this review, we provide critical insights into sirtuin pharmacology and illustrate their enzymatic activities and biological functions. Furthermore, we outline the most relevant sirtuin modulators in terms of their modes of action, structure-activity relationships, pharmacological effects, and clinical applications.

Redox imbalance driven epigenetic reprogramming and cardiovascular dysfunctions: phytocompounds for prospective epidrugs

BACKGROUND

Cardiovascular diseases (CVDs) are the major contributor to global mortality and are gaining incremental attention following the COVID-19 outbreak. Epigenetic events such as DNA methylation, histone modifications, and non-coding RNAs have a significant impact on the incidence and onset of CVDs. Altered redox status is one of the major causative factors that regulate epigenetic pathways linked to CVDs. Various bioactive phytocompounds used in alternative therapies including Traditional Chinese Medicines (TCM) regulate redox balance and epigenetic phenomena linked to CVDs. Phytocompound-based medications are in the limelight for the development of cost-effective drugs with the least side effects, which will have immense therapeutic applications.

PURPOSE

This review comprehends certain risk factors associated with CVDs and triggered by oxidative stress-driven epigenetic remodelling. Further, it critically evaluates the pharmacological efficacy of phytocompounds as inhibitors of HAT/HDAC and DNMTs as well as miRNAs regulator that lowers the incidence of CVDs, aiming for new candidates as prospective epidrugs.

METHODS

PRISMA flow approach has been adopted for systematic literature review. Different Journals, computational databases, search engines such as Google Scholar, PubMed, Science Direct, Scopus, and ResearchGate were used to collect online information for literature survey. Statistical information collected from the World Health Organization (WHO) site (https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds)) and the American Heart Association of Heart Disease and Stroke reported the international and national status of CVDs.

RESULTS

The meta-analysis of various studies is elucidated in the literature, shedding light on major risk factors such as socioeconomic parameters, which contribute highly to redox imbalance, epigenetic modulations, and CVDs. Going forward, redox imbalance driven epigenetic regulations include changes in DNA methylation status, histone modifications and non-coding RNAs expression pattern which further regulates global as well as promoter modification of various transcription factors leading to the onset of CVDs. Further, the role of various bioactive compounds used in herbal medicine, including TCM for redox regulation and epigenetic modifications are discussed. Pharmacological safety doses and different phases of clinical trials of these phytocompounds are elaborated on, which shed light on the acceptance of these phytocompounds as prospective drugs.

CONCLUSION

This review suggests a strong linkage between therapeutic and preventive measures against CVDs by targeting redox imbalance-driven epigenetic reprogramming using phytocompounds as prospective epidrugs. Future in-depth research is required to evaluate the possible molecular mechanisms behind the phytocompound-mediated epigenetic reprogramming and oxidative stress management during CVD progression.

Roles of Sirtuins in Cardiovascular Diseases: Mechanisms and Therapeutics

Cardiovascular diseases (CVDs) are experiencing a rapid surge and are widely recognized as the leading cause of mortality in the current aging society. Given the multifactorial etiology of CVDs, understanding the intricate molecular and cellular mechanisms is imperative. Over the past 2 decades, many scientists have focused on Sirtuins, a family of nicotinamide adenine dinucleotide-dependent deacylases. Sirtuins are highly conserved across species, from yeasts to primates, and play a crucial role in linking aging and diseases. Sirtuins participate in nearly all key physiological and pathological processes, ranging from embryogenic development to stress response and aging. Abnormal expression and activity of Sirtuins exist in many aging-related diseases, while their activation has shown efficacy in mitigating these diseases (eg, CVDs). In terms of research, this field has maintained fast, sustained growth in recent years, from fundamental studies to clinical trials. In this review, we present a comprehensive, up-to-date discussion on the biological functions of Sirtuins and their roles in regulating cardiovascular biology and CVDs. Furthermore, we highlight the latest advancements in utilizing Sirtuin-activating compounds and nicotinamide adenine dinucleotide boosters as potential pharmacological targets for preventing and treating CVDs. The key unresolved issues in the field-from the chemicobiological regulation of Sirtuins to Sirtuin-targeted CVD investigations-are also discussed. This timely review could be critical in understanding the updated knowledge of Sirtuin biology in CVDs and facilitating the clinical accessibility of Sirtuin-targeting interventions.

Circular RNA CHACR is involved in the pathogenesis of cardiac hypertrophy

Background: Circular RNAs (circRNAs) exhibit differential expression in cardiac hypertrophy; however, their functions and mechanisms remain largely unexplored. This study aimed to determine the involvement of circRNAs in the pathogenesis of myocardial hypertrophy. Methods: A mouse model of cardiac hypertrophy was established using transverse aortic constriction (TAC) and differentially expressed circRNAs were identified via high-throughput sequencing. To facilitate gene overexpression or knockdown, related viruses were injected into myocardial tissues of the mice. Cardiomyocyte hypertrophy was assessed using quantitative real-time PCR and immunofluorescence staining. RNA immunoprecipitation, RNA pull-down assay and fluorescence in situ hybridization were conducted to confirm the interaction between circRNAs and proteins. Protein expression and degradation were evaluated using cycloheximide-chase assay, immunoprecipitation, and western blotting. Results: Cardiac hypertrophy-associated circRNA (CHACR) was significantly downregulated in myocardial tissues from TAC mice. CHACR can attenuate cardiac hypertrophy through upregulating carnitine palmitoyltransferase-1b (CPT1b) expression. Mechanistically, CHACR directly interacted with CPT1b and decreased its protein degradation by inhibiting the ubiquitin-proteasome pathway to increase its expression in cardiomyocytes. Moreover, CPT1b overexpression decreased L-carnitine levels and inhibited the Jak2/Stat3 signaling pathway, which was associated with the pathogenesis of myocardial hypertrophy. Conclusions: CHACR attenuated cardiomyocyte hypertrophy by facilitating the expression of CPT1b, which plays a role in regulating the Jak2/Stat3 pathway via L-carnitine. CHACR may thus be a potential therapeutic target for pathological myocardial hypertrophy.

The enigmatic role of SIRT2 in the cardiovascular system: Deciphering its protective and detrimental actions to unlock new avenues for therapeutic intervention

Cardiovascular diseases (CVDs) are leading causes of mortality throughout the world, and hence, there is a critical need to elucidate their molecular mechanisms. The Sirtuin (SIRT) family of NAD+-dependent enzymes has recently been shown to play a critical role in cardiovascular health and disease, and several SIRT isoforms, especially SIRT1 and SIRT3, have been amply investigated. However, the precise function of SIRT2 is only partially explored. Here, we review the current understanding of the involvement of SIRT2 in various cardiovascular pathologies, such as cardiac hypertrophy, ischemia-reperfusion injury, diabetic cardiomyopathy, and vascular dysfunction, with emphasis placed on the context-dependent protective or deleterious actions of SIRT2, including its wide array of catalytic activities which span beyond deacetylation. Furthermore, the review uncovers several unresolved research gaps for SIRT2 mechanisms by which SIRT2 modulates cardiac and vascular function during development and aging, thereby paving the way for the discovery of novel therapeutic targets as well as SIRT2-targeted interventions in the prevention and treatment of various cardiovascular diseases.

Protective Effects of SIRT2 Inhibition on Cardiac Fibrosis

BACKGROUND

A primary factor in the pathogenesis of aging is oxidative stress, with cardiac inflammation and fibrosis being contributed to by increased oxidative stress as organisms age. Oxidative stress enhances the cardiac fibrotic signaling pathway, with reactive oxygen species inducing cardiac fibrosis through increased expression of the profibrotic factor transforming growth factor-beta 1 (TGF-β1). Furthermore, Wnt/β-catenin signaling pathway is implicated in interstitial fibrosis, which is associated with TGF-β. Sirtuin 2 (SIRT2) is expressed in heart tissue, with protective effects in pathological cardiac hypertrophy. We aimed to investigate the mechanisms of cardiac fibrosis in D-Galactose (D-Gal)-induced accelerated aging, focusing on TGF-β1, β-catenin, and SIRT2.

METHODS

A total of 30 young male Sprague-Dawley rats were randomly divided into 4 groups: control group, D-Gal group, D-Gal + 4% dimethyl sulfoxide (DMSO) group, and D-Gal + the SIRT2 inhibitor (AGK2) group. After 10 weeks, the rats were sacrificed, and their hearts were removed. SIRT2 expression levels were measured by western blot and gene expression levels of TGF-β1 and β-catenin by quantitative real-time polymerase chain reaction.

RESULTS

Transforming growth factor-beta 1 (TGF-β1) mRNA expression in heart tissue was higher in the D-Gal group compared to all other groups. β-catenin mRNA expression was higher in the D-Gal group than in the D-Gal + AGK2 group. SIRT2 protein expression was higher in the D-Gal + DMSO group compared to the control group. Sirtuin 2 expression was lower in the D-Gal + AGK2 group compared to the D-Gal and D-Gal + DMSO groups.

CONCLUSION

Sirtuin 2 inhibition attenuates fibrosis, as evidenced by the downregulation of TGF-β1 and β-catenin. Thus, targeting SIRT2 may represent a potential therapeutic strategy for diseases characterized by cardiac fibrosis in the future.

Involvement of TGF-β, mTOR, and inflammatory mediators in aging alterations during myxomatous mitral valve disease in a canine model

Inflammaging, a state of chronic low-grade inflammation associated with aging, has been linked to the development and progression of various disorders. Cellular senescence, a state of irreversible growth arrest, is another characteristic of aging that contributes to the pathogenesis of cardiovascular pathology. Senescent cells accumulate in tissues over time and secrete many inflammatory mediators, further exacerbating the inflammatory environment. This senescence-associated secretory phenotype can promote tissue dysfunction and remodeling, ultimately leading to the development of age-related cardiovascular pathologies, such as mitral valve myxomatous degeneration. The species-specific form of canine myxomatous mitral valve disease (MMVD) provides a unique opportunity to investigate the early causes of induction of ECM remodeling in mitral valve leaflets in the human form of MMVD. Studies have shown that in both humans and dogs, the microenvironment of the altered leaflets is inflammatory. More recently, the focus has been on the mechanisms leading to the transformation of resting VICs (qVICs) to myofibroblast-like VICs (aVICs). Cells affected by stress fall into a state of cell cycle arrest and become senescent cells. aVICs, under the influence of TGF-β signaling pathways and the mTOR complex, enhance ECM alteration and accumulation of systemic inflammation. This review aims to create a fresh new view of the complex interaction between aging, inflammation, immunosenescence, and MMVD in a canine model, as the domestic dog is a promising model of human aging and age-related diseases.

Downregulation of MLF1 safeguards cardiomyocytes against senescence-associated chromatin opening

Aging-associated cardiac hypertrophy (AACH) increases susceptibility to heart failure in the elderly. Chromatin remodeling contributes to the gene reprogramming in AACH; however, the intrinsic regulations remain elusive. We performed a transcriptome analysis for AACH in comparison with pressure-overload-induced pathological cardiac hypertrophy in mice and identified myeloid leukemia factor 1 (MLF1) as an aging-sensitive factor whose expression was reduced during aging but could be reversed by anti-aging administrations. In human AC16 cardiomyocytes, silencing MLF1 suppressed H2O2-induced cell senescence while the phenotype was exacerbated by MLF1 overexpression. RNA-seq analysis revealed that MLF1 functioned as a transcription activator, regulating genomic-clustered genes that mainly involved in inflammation and development. ATAC-seq analysis showed a prominent reduction in chromatin accessibility at the promoter regions of senescence effectors, like IL1B and p21, after MLF1 knockdown. Despite a potential interaction of MLF1 with the histone methyltransferase PRC2, its inhibition failed to reverse the impact of MLF1 knockdown. Instead, MLF1-mediated regulation was blunted by inhibiting the acetyltransferase EP300. CUT&Tag analysis showed that MLF1 bound to target promoters and recruited EP300 to promote H3K27ac deposition. Collectively, we identify MLF1 as a pro-aging epigenetic orchestrator that recruits EP300 to facilitate opening of the condensed chromatin encompassing senescence effectors.

Mitochondrial SIRT2-mediated CPT2 deacetylation prevents diabetic cardiomyopathy by impeding cardiac fatty acid oxidation

Dysregulated energy metabolism, particularly lipid metabolism disorders, has been identified as a key factor in the development of diabetic cardiomyopathy (DCM). Sirtuin 2 (SIRT2) is a deacetylase involved in the regulation of metabolism and cellular energy homeostasis, yet its role in the progression of DCM remains unclear. We observed significantly reduced SIRT2 expression in DCM model mice. Cardiac-specific overexpression of SIRT2 protected mice from streptozotocin/high-fat diet (STZ/HFD)-induced insulin resistance (IR), cell apoptosis, and cardiac dysfunction, whereas its downregulation exacerbated these conditions. Moreover, we found that SIRT2 regulated cardiac lipid accumulation and fatty acid oxidation (FAO), and identified its localization in cardiac mitochondria. Mechanistically, we determined carnitine palmitoyltransferase 2 (CPT2) as a critical substrate of SIRT2, which is implicated in DCM. SIRT2-mediated deacetylation at K239 enhanced CPT2 ubiquitination, resulting in decreased protein stability and subsequent inhibition of FAO and reactive oxygen species (ROS) production. Taken together, these findings suggest that the SIRT2/CPT2 signaling pathway plays a crucial role in DCM progression.

The role of cardiomyocyte senescence in cardiovascular diseases: A molecular biology update

Cardiovascular diseases (CVD) are the leading cause of death worldwide, and advanced age is a main contributor to the prevalence of CVD. Cellular senescence is an irreversible state of cell cycle arrest that occurs in old age or after cells encounter various stresses. Senescent cells not only result in the reduction of cellular function, but also produce senescence-associated secretory phenotype (SASP) to affect surrounding cells and tissue microenvironment. There is increasing evidence that the gradual accumulation of senescent cardiomyocytes is causally involved in the decline of cardiovascular system function. To highlight the role of senescent cardiomyocytes in the pathophysiology of age-related CVD, we first introduced that senescent cardiomyoyctes can be identified by structural changes and several senescence-associated biomarkers. We subsequently provided a comprehensive summary of existing knowledge, outlining the compelling evidence on the relationship between senescent cardiomyocytes and age-related CVD phenotypes. In addition, we discussed that the significant therapeutic potential represented by the prevention of accelerated senescent cardiomyocytes, and the current status of some existing geroprotectors in the prevention and treatment of age-related CVD. Together, the review summarized the role of cardiomyocyte senescence in CVD, and explored the molecular knowledge of senescent cardiomyocytes and their potential clinical significance in developing senescent-based therapies, thereby providing important insights into their biology and potential therapeutic exploration.

Histone deacetylases: Regulation of vascular homeostasis via endothelial cells and vascular smooth muscle cells and the role in vascular pathogenesis

Histone deacetylases (HDACs) are proteases that play a key role in chromosome structural modification and gene expression regulation, and the involvement of HDACs in cancer, the nervous system, and the metabolic and immune system has been well reviewed. Our understanding of the function of HDACs in the vascular system has recently progressed, and a significant variety of HDAC inhibitors have been shown to be effective in the treatment of vascular diseases. However, few reviews have focused on the role of HDACs in the vascular system. In this study, the role of HDACs in the regulation of the vascular system mainly involving endothelial cells and vascular smooth muscle cells was discussed based on recent updates, and the role of HDACs in different vascular pathogenesis was summarized as well. Furthermore, the therapeutic effects and prospects of HDAC inhibitors were also addressed in this review.

Current concepts in the epigenetic regulation of cardiac fibrosis

Cardiac fibrosis is a significant driver of congestive heart failure, a syndrome that continues to affect a growing patient population globally. Cardiac fibrosis results from a constellation of complex processes at the transcription, receptor, and signaling axes levels. Various mediators and signaling cascades, such as the transformation growth factor-beta pathway, have been implicated in the pathophysiology of cardiac tissue fibrosis. Our understanding of these markers and pathways has improved in recent years as more advanced technologies and assays have been developed, allowing for better delineation of the crosstalk between specific factors. There is mounting evidence suggesting that epigenetic modulation plays a pivotal role in the progression of cardiac fibrosis. Transcriptional regulation of key pro- and antifibrotic pathways can accentuate or blunt the rate and extent of fibrosis at the tissue level. Exosomes, micro-RNAs, and long noncoding RNAs all belong to factors that can impact the epigenetic signature in cardiac fibrosis. Herein, we comprehensively review the latest literature about exosomes, their contents, and cardiac fibrosis. In doing so, we highlight the specific transcriptional factors with pro- or antifibrotic properties. We also assimilate the data supporting these mediators' potential utility as diagnostic or prognostic biomarkers. Finally, we offer insight into where further work can be done to fill existing gaps to translate preclinical findings better and improve clinical outcomes.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

The aging heart in focus: The advanced understanding of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for 50 % of heart failure (HF) cases, making it the most common type of HF, and its prevalence continues to increase in the aging society. HFpEF is a systemic syndrome resulting from many risk factors, such as aging, metabolic syndrome, and hypertension, and its clinical features are highly heterogeneous in different populations. HFpEF syndrome involves the dysfunction of multiple organs, including the heart, lung, muscle, and vascular system. The heart shows dysfunction of various cells, including cardiomyocytes, endothelial cells, fibroblasts, adipocytes, and immune cells. The complex etiology and pathobiology limit experimental research on HFpEF in animal models, delaying a comprehensive understanding of the mechanisms and making treatment difficult. Recently, many scientists and cardiologists have attempted to improve the clinical outcomes of HFpEF. Recent advances in clinically related animal models and systemic pathology studies have improved our understanding of HFpEF, and clinical trials involving sodium-glucose cotransporter 2 inhibitors have significantly enhanced our confidence in treating HFpEF. This review provides an updated comprehensive discussion of the etiology and pathobiology, molecular and cellular mechanisms, preclinical animal models, and therapeutic trials in animals and patients to enhance our understanding of HFpEF and improve clinical outcomes.

Drugs Targeting Sirtuin 2 Exhibit Broad-Spectrum Anti-Infective Activity

Direct-acting anti-infective drugs target pathogen-coded gene products and are a highly successful therapeutic paradigm. However, they generally target a single pathogen or family of pathogens, and the targeted organisms can readily evolve resistance. Host-targeted agents can overcome these limitations. One family of host-targeted, anti-infective agents modulate human sirtuin 2 (SIRT2) enzyme activity. SIRT2 is one of seven human sirtuins, a family of NAD+-dependent protein deacylases. It is the only sirtuin that is found predominantly in the cytoplasm. Multiple, structurally distinct SIRT2-targeted, small molecules have been shown to inhibit the replication of both RNA and DNA viruses, as well as intracellular bacterial pathogens, in cell culture and in animal models of disease. Biochemical and X-ray structural studies indicate that most, and probably all, of these compounds act as allosteric modulators. These compounds appear to impact the replication cycles of intracellular pathogens at multiple levels to antagonize their replication and spread. Here, we review SIRT2 modulators reported to exhibit anti-infective activity, exploring their pharmacological action as anti-infectives and identifying questions in need of additional study as this family of anti-infective agents advances to the clinic.

Crotonylation of NAE1 Modulates Cardiac Hypertrophy via Gelsolin Neddylation

BACKGROUND

Cardiac hypertrophy and its associated remodeling are among the leading causes of heart failure. Lysine crotonylation is a recently discovered posttranslational modification whose role in cardiac hypertrophy remains largely unknown. NAE1 (NEDD8 [neural precursor cell expressed developmentally downregulated protein 8]-activating enzyme E1 regulatory subunit) is mainly involved in the neddylation modification of protein targets. However, the function of crotonylated NAE1 has not been defined. This study aims to elucidate the effects and mechanisms of NAE1 crotonylation on cardiac hypertrophy.

METHODS

Crotonylation levels were detected in both human and mouse subjects with cardiac hypertrophy through immunoprecipitation and Western blot assays. Tandem mass tag (TMT)-labeled quantitative lysine crotonylome analysis was performed to identify the crotonylated proteins in a mouse cardiac hypertrophic model induced by transverse aortic constriction. We generated NAE1 knock-in mice carrying a crotonylation-defective K238R (lysine to arginine mutation at site 238) mutation (NAE1 K238R) and NAE1 knock-in mice expressing a crotonylation-mimicking K238Q (lysine to glutamine mutation at site 238) mutation (NAE1 K238Q) to assess the functional role of crotonylation of NAE1 at K238 in pathological cardiac hypertrophy. Furthermore, we combined coimmunoprecipitation, mass spectrometry, and dot blot analysis that was followed by multiple molecular biological methodologies to identify the target GSN (gelsolin) and corresponding molecular events contributing to the function of NAE1 K238 (lysine residue at site 238) crotonylation.

RESULTS

The crotonylation level of NAE1 was increased in mice and patients with cardiac hypertrophy. Quantitative crotonylomics analysis revealed that K238 was the main crotonylation site of NAE1. Loss of K238 crotonylation in NAE1 K238R knock-in mice attenuated cardiac hypertrophy and restored the heart function, while hypercrotonylation mimic in NAE1 K238Q knock-in mice significantly enhanced transverse aortic constriction-induced pathological hypertrophic response, leading to impaired cardiac structure and function. The recombinant adenoviral vector carrying NAE1 K238R mutant attenuated, while the K238Q mutant aggravated Ang II (angiotensin II)-induced hypertrophy. Mechanistically, we identified GSN as a direct target of NAE1. K238 crotonylation of NAE1 promoted GSN neddylation and, thus, enhanced its protein stability and expression. NAE1 crotonylation-dependent increase of GSN promoted actin-severing activity, which resulted in adverse cytoskeletal remodeling and progression of pathological hypertrophy.

CONCLUSIONS

Our findings provide new insights into the previously unrecognized role of crotonylation on nonhistone proteins during cardiac hypertrophy. We found that K238 crotonylation of NAE1 plays an essential role in mediating cardiac hypertrophy through GSN neddylation, which provides potential novel therapeutic targets for pathological hypertrophy and cardiac remodeling.

Cardiomyocyte-derived small extracellular vesicle: a new mechanism driving diabetic cardiac fibrosis and cardiomyopathy

Rationale: Diabetic cardiomyopathy is one of the major diabetic cardiovascular complications in which fibrosis plays a critical pathogenetic role. However, the precise mechanisms by which diabetes triggers cardiac fibrosis in the heart remain elusive. Small extracellular vesicles (sEVs) play an important role in the cellular communication. Nevertheless, whether and how diabetes may adversely alter sEVs-mediated cardiomyocyte-fibroblast communication, promoting diabetic cardiac fibrosis and contributing to diabetic cardiomyopathy, has not been previously investigated. Methods and results: High-fat diet (HFD)-induced and genetic (db/db) type 2 diabetic models were utilized. Cardiomyocyte sEVs (Myo-sEVs) were isolated by ultracentrifugation. Normal cardiomyocyte-derived Myo-sEVs attenuated diabetic cardiac fibrosis in vitro and in vivo and improved cardiac diastolic function. In contrast, diabetic cardiomyocyte-derived Myo-sEVs significantly exacerbated diabetic cardiac fibrosis and worsened diastolic function. Unbiased miRNA screening analysis revealed that miR-194-3p was significantly reduced in diabetic Myo-sEVs. Additional in vitro and in vivo experiments demonstrated that miR-194-3p is a novel upstream molecule inhibiting TGFβR2 expression and blocking fibroblast-myofibroblast conversion. Administration of miR-194-3p mimic or agomiR-194-3p significantly reduced diabetic cardiac fibrosis in vitro and in vivo, and attenuated diabetic cardiomyopathy. Conclusion: Our study demonstrates for the first time that cardiomyocyte-derived miR194-3p inhibits TGFβ-mediated fibroblast-to-myofibroblast conversion, acting as an internal break against cardiac fibrosis. Diabetic downregulation of sEV-mediated miR-194-3p delivery from cardiomyocytes to fibroblasts contributes to diabetic cardiac fibrosis and diabetic cardiomyopathy. Pharmacological or genetic restoration of this system may be a novel therapy against diabetic cardiomyopathy.

SIRT1: a novel regulator in colorectal cancer

The class-III histone deacetylase SIRT1 is the most extensively investigated sirtuin deacetylase. It is resistant to the broad deacetylase inhibitor trichostatin A and depends on oxidized nicotinamide adenine nucleotide (NAD+). SIRT1 plays a crucial role in the tumorigenesis of numerous types of cancers, including colorectal cancer (CRC). Accumulating evidence indicates that SIRT1 is a therapeutic target for CRC; however, the function and underlying mechanism of SIRT1 in CRC still need to be elucidated. Herein, we provide a detailed and updated review to illustrate that SIRT1 regulates many processes that go awry in CRC cells, such as apoptosis, autophagy, proliferation, migration, invasion, metastasis, oxidative stress, resistance to chemo-radio therapy, immune evasion, and metabolic reprogramming. Moreover, we closely link our review to the clinical practice of CRC treatment, summarizing the mechanisms and prospects of SIRT1 inhibitors in CRC therapy. SIRT1 inhibitors as monotherapy in CRC or in combination with chemotherapy, radiotherapy, and immune therapies are comprehensively discussed. From epigenetic regulation to its potential therapeutic effect, we hope to offer novel insights and a comprehensive understanding of SIRT1's role in CRC.

Artesunate attenuates isoprenaline induced cardiac hypertrophy in rats via SIRT1 inhibiting NF-κB activation

Cardiac Hypertrophy is an adaptive response of the body to physiological and pathological stimuli, which increases cardiomyocyte size, thickening of cardiac muscles and progresses to heart failure. Downregulation of SIRT1 in cardiomyocytes has been linked with the pathogenesis of cardiac hypertrophy. The present study aimed to investigate the effect of Artesunate against isoprenaline induced cardiac hypertrophy in rats via SIRT1 inhibiting NF-κB activation. Experimental cardiac hypertrophy was induced in rats by subcutaneous administration of isoprenaline (5 mg/kg) for 14 days. Artesunate was administered simultaneously for 14 days at a dose of 25 mg/kg and 50 mg/kg. Artesunate administration showed significant dose dependent attenuation in mean arterial pressure, electrocardiogram, hypertrophy index and left ventricular wall thickness compared to the disease control group. It also alleviated cardiac injury biomarkers and oxidative stress. Histological observation showed amelioration of tissue injury in the artesunate treated groups compared to the disease control group. Further, artesunate treatment increased SIRT1 expression and decreased NF-kB expression in the heart. The results of the study show the cardioprotective effect of artesunate via SIRT1 inhibiting NF-κB activation in cardiomyocytes.

Targeting SIRT2 in Aging-Associated Fibrosis Pathophysiology

Aging is a complex biological process that involves multi-level structural and physiological changes. Aging is a major risk factor for many chronic diseases. The accumulation of senescent cells changes the tissue microenvironment and is closely associated with the occurrence and development of tissue and organ fibrosis. Fibrosis is the result of dysregulated tissue repair response in the development of chronic inflammatory diseases. Recent studies have clearly indicated that SIRT2 is involved in regulating the progression of fibrosis, making it a potential target for anti-fibrotic drugs. SIRT2 is a NAD+ dependent histone deacetylase, shuttling between nucleus and cytoplasm, and is highly expressed in liver, kidney and heart, playing an important role in the occurrence and development of aging and fibrosis. Therefore, we summarized the role of SIRT2 in liver, kidney and cardiac fibrosis during aging.

Metformin prevents the onset and progression of intervertebral disc degeneration: New insights and potential mechanisms (Review)

Metformin has been the go‑to medical treatment for addressing type 2 diabetes mellitus (T2DM) as a frontline oral antidiabetic. Obesity, cancer and bone deterioration are linked to T2DM, which is considered a metabolic illness. Numerous diseases associated with T2DM, such as tumours, cardiovascular disease and bone deterioration, may be treated with metformin. Intervertebral disc degeneration (IVDD) is distinguished by degeneration of the spinal disc, accompanied by the gradual depletion of proteoglycans and water in the nucleus pulposus (NP) of the IVD, resulting in lower back pain. The therapeutic effect of metformin on IVDD has also attracted much attention. By stimulating AMP‑activated kinase, metformin could enhance autophagy and suppress cell senescence, apoptosis and inflammation, thus effectively delaying IVDD. The present review aimed to systematically explain the development of IVDD and mechanism of metformin in the treatment and prevention of IVDD to provide a reference for the clinical application of metformin as adjuvant therapy in the treatment of IVDD.

1,8-cineole ameliorates experimental diabetic angiopathy by inhibiting NLRP3 inflammasome-mediated pyroptosis in HUVECs via SIRT2

Accumulating evidence strongly support the key role of NLRP3-mediated pyroptosis in the pathogenesis and progression of vascular endothelial dysfunction associated with diabetes mellitus. Various studies have demonstrated that the activation or upregulation of Silent Information Regulation 2 homolog 2 (SIRT2) exerts inhibitory effect on the expression of NLRP3. Although 1,8-cineole has been found to protect against endothelial dysfunction and cardiovascular diseases, its role and mechanism in diabetic angiopathy remain unknown. Therefore, the aim of this study was to investigate the ameliorative effect of 1,8-cineole through SIRT2 on pyroptosis associated with diabetic angiopathy in human umbilical vein endothelial cells (HUVECs) and to elucidate the underlying mechanism. The findings revealed that 1,8-cineole exhibited a protective effect against vascular injury and ameliorated pathological alterations in the thoracic aorta of diabetic mice. Moreover, it effectively mitigated pyroptosis induced by palmitic acid-high glucose (PA-HG) in HUVECs. Treatment with 1,8-cineole effectively restored the reduced levels of SIRT2 and suppressed the elevated expression of pyroptosis-associated proteins. Additionally, our findings demonstrated the occurrence of NLRP3 deacetylation and the physical interaction between NLRP3 and SIRT2. The SIRT2 inhibitor AGK2 and siRNA-SIRT2 effectively attenuated the effect of 1,8-cineole on NLRP3 deacetylation in HUVECs and compromised its inhibitory effect against pyroptosis in HUVECs. However, overexpression of SIRT2 inhibited PA-HG-induced pyroptosis in HUVECs. 1,8-Cineole inhibited the deacetylation of NLRP3 by regulating SIRT2, thereby reducing pyroptosis in HUVECs. In conclusion, our findings suggest that PA-HG-induced pyroptosis in HUVECs plays a crucial role in the development of diabetic angiopathy, which can be mitigated by 1,8-cineole.

SIRT-associated attenuation of cellular senescence in vascular wall

This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.

Sulfenylation of ERK1/2: A novel mechanism for SO2-mediated inhibition of cardiac fibroblast proliferation

Background

Endogenous sulfur dioxide (SO2) plays a crucial role in protecting heart from myocardial fibrosis by inhibiting the excessive growth of cardiac fibroblasts. This study aimed to investigate potential mechanisms by which SO2 suppressed myocardial fibrosis.

Methods and results

Mouse model of angiotensin II (Ang II)-induced cardiac fibrosis and cell model of Ang II-stimulated cardiac fibroblast proliferation were employed. Our findings discovered that SO2 mitigated the aberrant phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) induced by Ang II, leading to a reduction of fibroblast proliferation. Mechanistically, for the first time, we found that SO2 sulfenylated ERK1/2, and inhibited ERK1/2 phosphorylation and cardiac fibroblast proliferation, while a sulfhydryl reducing agent dithiothreitol (DTT) reversed the above effects of SO2. Furthermore, mutant ERK1C183S (cysteine 183 to serine) abolished the sulfenylation of ERK by SO2, thereby preventing the inhibitory effects of SO2 on ERK1 phosphorylation and cardiac fibroblast proliferation.

Conclusion

Our study suggested that SO2 inhibited cardiac fibroblast proliferation by sulfenylating ERK1/2 and subsequently suppressing ERK1/2 phosphorylation. These new findings might enhance the understanding of the mechanisms underlying myocardial fibrosis and emphasize the potential of SO2 as a novel therapeutic target for myocardial fibrosis.

Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions

Cardiovascular diseases (CVDs) remain a leading global cause of morbidity and mortality. These diseases have a multifaceted nature being influenced by a multitude of biochemical, genetic, environmental, and behavioral factors. Epigenetic modifications have a crucial role in the onset and progression of CVD. Epigenetics, which regulates gene activity without altering the DNA's primary structure, can modulate cardiovascular homeostasis through DNA methylation, histone modification, and non-coding RNA regulation. The effects of environmental stimuli on CVD are mediated by epigenetic changes, which can be reversible and, hence, are susceptible to pharmacological interventions. This represents an opportunity to prevent diseases by targeting harmful epigenetic modifications. Factors such as high-fat diets or nutrient deficiencies can influence epigenetic enzymes, affecting fetal growth, metabolism, oxidative stress, inflammation, and atherosclerosis. Recent studies have shown that plant-derived bioactive compounds can modulate epigenetic regulators and inflammatory responses, contributing to the cardioprotective effects of diets. Understanding these nutriepigenetic effects and their reversibility is crucial for developing effective interventions to combat CVD. This review delves into the general mechanisms of epigenetics, its regulatory roles in CVD, and the potential of epigenetics as a CVD therapeutic strategy. It also examines the role of epigenetic natural compounds (ENCs) in CVD and their potential as intervention tools for prevention and therapy.

Inhalable cardiac targeting peptide modified nanomedicine prevents pressure overload heart failure in male mice

Heart failure causes considerable morbidity and mortality worldwide. Clinically applied drugs for the treatment of heart failure are still severely limited by poor delivery efficiency to the heart and off-target consumption. Inspired by the high heart delivery efficiency of inhaled drugs, we present an inhalable cardiac-targeting peptide (CTP)-modified calcium phosphate (CaP) nanoparticle for the delivery of TP-10, a selective inhibitor of PDE10A. The CTP modification significantly promotes cardiomyocyte and fibroblast targeting during the pathological state of heart failure in male mice. TP-10 is subsequently released from TP-10@CaP-CTP and effectively attenuates cardiac remodelling and improved cardiac function. In view of these results, a low dosage (2.5 mg/kg/2 days) of inhaled medication exerted good therapeutic effects without causing severe lung injury after long-term treatment. In addition, the mechanism underlying the amelioration of heart failure is investigated, and the results reveal that the therapeutic effects of this system on cardiomyocytes and cardiac fibroblasts are mainly mediated through the cAMP/AMPK and cGMP/PKG signalling pathways. By demonstrating the targeting capacity of CTP and verifying the biosafety of inhalable CaP nanoparticles in the lung, this work provides a perspective for exploring myocardium-targeted therapy and presents a promising clinical strategy for the long-term management of heart failure.

The SIRT2-AMPK axis regulates autophagy induced by acute liver failure

This study explores the role of SIRT2 in regulating autophagy and its interaction with AMPK in the context of acute liver failure (ALF). This study investigated the effects of SIRT2 and AMPK on autophagy in ALF mice and TAA-induced AML12 cells. The results revealed that the liver tissue in ALF model group had a lot of inflammatory cell infiltration and hepatocytes necrosis, which were reduced by SIRT2 inhibitor AGK2. In comparison to normal group, the level of SIRT2, P62, MDA, TOS in TAA group were significantly increased, which were decreased in AGK2 treatment. Compared with normal group, the expression of P-PRKAA1, Becilin1 and LC3B-II was decreased in TAA group. However, AGK2 enhanced the expression of P-PRKAA1, Becilin1 and LC3B-II in model group. Overexpression of SIRT2 in AML12 cell resulted in decreased P-PRKAA1, Becilin1 and LC3B-II level, enhanced the level of SIRT2, P62, MDA, TOS. Overexpression of PRKAA1 in AML12 cell resulted in decreased SIRT2, TOS and MDA level and triggered more autophagy. In conclusion, the data suggested the link between AMPK and SIRT2, and reveals the important role of AMPK and SIRT2 in autophagy on acute liver failure.

Research progress on the role and mechanism of Sirtuin family in doxorubicin cardiotoxicity

BACKGROUND

Doxorubicin (DOX) is a widely utilized anthracycline chemotherapy drug in cancer treatment, yet its efficacy is hindered by both short-term and long-term cardiotoxicity. Although oxidative stress, inflammation and mitochondrial dysfunction are established factors in DOX-induced cardiotoxicity, the precise molecular pathways remain elusive. Further exploration of the pathogenesis and identification of novel molecular targets are imperative. Recent studies have implicated the Sirtuins family in various physiological and pathological processes, suggesting their potential in ameliorating DOX-induced cardiotoxicity. Moreover, research on Sirtuins has discovered small-molecule compounds or medicinal plants with regulatory effects, representing a notable advancement in preventing and treating DOX-induced cardiac injury.

PURPOSE

In this review, we delve into the pathogenesis of DOX-induced cardiotoxicity and explore the therapeutic effects of Sirtuins in mitigating this condition, along with the associated molecular mechanisms. Furthermore, we delineate the roles and mechanisms of small-molecule regulators of Sirtuins in the prevention and treatment of DOX-induced cardiotoxicity.

STUDY-DESIGN/METHODS

Data for this review were sourced from various scientific databases (such as Web of Science, PubMed and Science Direct) up to March 2024. Search terms included "Sirtuins," "DOX-induced cardiotoxicity," "DOX," "Sirtuins regulators," "histone deacetylation," among others, as well as several combinations thereof.

RESULTS

Members of the Sirtuins family regulate both the onset and progression of DOX-induced cardiotoxicity through anti-inflammatory, antioxidative stress and anti-apoptotic mechanisms, as well as by maintaining mitochondrial stability. Moreover, natural plant-derived active compounds such as Resveratrol (RES), curcumin, berberine, along with synthetic small-molecule compounds like EX527, modulate the expression and activity of Sirtuins.

CONCLUSION

The therapeutic role of the Sirtuins family in mitigating DOX-induced cardiotoxicity represents a potential molecular target. However, further research is urgently needed to elucidate the relevant molecular mechanisms and to assess the safety and biological activity of Sirtuins regulators. This review offers an in-depth understanding of the therapeutic role of the Sirtuins family in mitigating DOX-induced cardiotoxicity, providing a preliminary basis for the clinical application of Sirtuins regulators in this condition.

LKB1 biology: assessing the therapeutic relevancy of LKB1 inhibitors

Liver Kinase B1 (LKB1), encoded by Serine-Threonine Kinase 11 (STK11), is a master kinase that regulates cell migration, polarity, proliferation, and metabolism through downstream adenosine monophosphate-activated protein kinase (AMPK) and AMPK-related kinase signalling. Since genetic screens identified STK11 mutations in Peutz-Jeghers Syndrome, STK11 mutants have been implicated in tumourigenesis labelling it as a tumour suppressor. In support of this, several compounds reduce tumour burden through upregulating LKB1 signalling, and LKB1-AMPK agonists are cytotoxic to tumour cells. However, in certain contexts, its role in cancer is paradoxical as LKB1 promotes tumour cell survival by mediating resistance against metabolic and oxidative stressors. LKB1 deficiency has also enhanced the selectivity and cytotoxicity of several cancer therapies. Taken together, there is a need to develop LKB1-specific pharmacological compounds, but prior to developing LKB1 inhibitors, further work is needed to understand LKB1 activity and regulation. However, investigating LKB1 activity is strenuous as cell/tissue type, mutations to the LKB1 signalling pathway, STE-20-related kinase adaptor protein (STRAD) binding, Mouse protein 25-STRAD binding, splicing variants, nucleocytoplasmic shuttling, post-translational modifications, and kinase conformation impact the functional status of LKB1. For these reasons, guidelines to standardize experimental strategies to study LKB1 activity, associate proteins, spliced isoforms, post-translational modifications, and regulation are of upmost importance to the development of LKB1-specific therapies. Therefore, to assess the therapeutic relevancy of LKB1 inhibitors, this review summarizes the importance of LKB1 in cell physiology, highlights contributors to LKB1 activation, and outlines the benefits and risks associated with targeting LKB1.

Caloric restriction, Sirtuins, and cardiovascular diseases

ABSTRACT

Caloric restriction (CR) is a well-established dietary intervention known to extend healthy lifespan and exert positive effects on aging-related diseases, including cardiovascular conditions. Sirtuins, a family of nicotinamide adenine dinucleotide (NAD + )-dependent histone deacetylases, have emerged as key regulators of cellular metabolism, stress responses, and the aging process, serving as energy status sensors in response to CR. However, the mechanism through which CR regulates Sirtuin function to ameliorate cardiovascular disease remains unclear. This review not only provided an overview of recent research investigating the interplay between Sirtuins and CR, specifically focusing on their potential implications for cardiovascular health, but also provided a comprehensive summary of the benefits of CR for the cardiovascular system mediated directly via Sirtuins. CR has also been shown to have considerable impact on specific metabolic organs, leading to the production of small molecules that enter systemic circulation and subsequently regulate Sirtuin activity within the cardiovascular system. The direct and indirect effects of CR offer a potential mechanism for Sirtuin modulation and subsequent cardiovascular protection. Understanding the interplay between CR and Sirtuins will provide new insights for the development of interventions to prevent and treat cardiovascular diseases.

Meteorin-like (METRNL) attenuates hypertensive induced cardiac hypertrophy by inhibiting autophagy via activating BRCA2

Hypertension, a prevalent cardiovascular ailment globally, can precipitate numerous complications, notably hypertensive cardiomyopathy. Meteorin-like (METRNL) is demonstrated to possess potential protective properties on cardiovascular diseases. However, its specific role and underlying mechanism in hypertensive myocardial hypertrophy remain elusive. Spontaneously hypertensive rats (SHRs) served as hypertensive models to explore the effects of METRNL on hypertension and its induced myocardial hypertrophy. The research results indicate that, in contrast to Wistar-Kyoto (WKY) rats, SHRs exhibit significant symptoms of hypertension and myocardial hypertrophy, but cardiac-specific overexpression (OE) of METRNL can partially ameliorate these symptoms. In H9c2 cardiomyocytes, METRNL suppresses Ang II-induced autophagy by controlling the BRCA2/Akt/mTOR signaling pathway. But when BRCA2 expression is knocked down, this effect will be suppressed. Collectively, METRNL emerges as a potential therapeutic target for hypertensive cardiomyopathy.

Endothelial H2S-AMPK dysfunction upregulates the angiocrine factor PAI-1 and contributes to lung fibrosis

Dysfunction of the vascular angiocrine system is critically involved in regenerative defects and fibrosis of injured organs. Previous studies have identified various angiocrine factors and found that risk factors such as aging and metabolic disorders can disturb the vascular angiocrine system in fibrotic organs. One existing key gap is what sense the fibrotic risk to modulate the vascular angiocrine system in organ fibrosis. Here, using human and mouse data, we discovered that the metabolic pathway hydrogen sulfide (H2S)-AMP-activated protein kinase (AMPK) is a sensor of fibrotic stress and serves as a key mechanism upregulating the angiocrine factor plasminogen activator inhibitor-1 (PAI-1) in endothelial cells to participate in lung fibrosis. Activation of the metabolic sensor AMPK was inhibited in endothelial cells of fibrotic lungs, and AMPK inactivation was correlated with enriched fibrotic signature and reduced lung functions in humans. The inactivation of endothelial AMPK accelerated lung fibrosis in mice, while the activation of endothelial AMPK with metformin alleviated lung fibrosis. In fibrotic lungs, endothelial AMPK inactivation led to YAP activation and overexpression of the angiocrine factor PAI-1, which was positively correlated with the fibrotic signature in human fibrotic lungs and inhibition of PAI-1 with Tiplaxtinin mitigated lung fibrosis. Further study identified that the deficiency of the antioxidative gas metabolite H2S accounted for the inactivation of AMPK and activation of YAP-PAI-1 signaling in endothelial cells of fibrotic lungs. H2S deficiency was involved in human lung fibrosis and H2S supplement reversed mouse lung fibrosis in an endothelial AMPK-dependent manner. These findings provide new insight into the mechanism underlying the deregulation of the vascular angiocrine system in fibrotic organs.

Spinal sirtuin 2 attenuates bone cancer pain by deacetylating FoxO3a

Bone cancer pain (BCP) is refractory to currently used analgesics. Recently, sirtuin 2 (SIRT2) was reported to play a vital role in neuropathic pain but its role in BCP remains unknown. It was hypothesized that spinal SIRT2 attenuates BCP by deacetylating FoxO3a and suppressing oxidative stress. The mouse model of BCP established by injecting tumor cells into the intramedullary space of the femur demonstrated that spinal SIRT2 and FoxO3a were downregulated in BCP development. Intrathecal administration of LV-SIRT2 reduced pain hypersensitivity (mechanical and thermal nociception) in BCP mice. Spinal SIRT2 overexpression upregulated FoxO3a and antioxidant genes (SOD2 and catalase) and inhibited FoxO3a acetylation, phosphorylation, and ubiquitination. Moreover, intrathecal administration of SIRT2 shRNA induced pain hypersensitivity in normal mice. Spinal SIRT2 knockdown downregulated FoxO3a and antioxidant genes and increased FoxO3a acetylation, phosphorylation, and ubiquitination. In summary, spinal SIRT2 increases FoxO3a expression in BCP mice and inhibits oxidative stress by deacetylating FoxO3a and further reducing FoxO3a phosphorylation, ubiquitination, and degradation, leading to BCP relief.

The role of deubiquitinases in cardiac disease

Deubiquitinases are a group of proteins that identify and digest monoubiquitin chains or polyubiquitin chains attached to substrate proteins, preventing the substrate protein from being degraded by the ubiquitin-proteasome system. Deubiquitinases regulate cellular autophagy, metabolism and oxidative stress by acting on different substrate proteins. Recent studies have revealed that deubiquitinases act as a critical regulator in various cardiac diseases, and control the onset and progression of cardiac disease through a board range of mechanism. This review summarizes the function of different deubiquitinases in cardiac disease, including cardiac hypertrophy, myocardial infarction and diabetes mellitus-related cardiac disease. Besides, this review briefly recapitulates the role of deubiquitinases modulators in cardiac disease, providing the potential therapeutic targets in the future.

New Perspectives on the Role and Therapeutic Potential of Melatonin in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. It is essential to develop novel interventions to prevent/delay CVDs by targeting their fundamental cellular and molecular processes. Melatonin is a small indole molecule acting both as a hormone of the pineal gland and as a local regulator molecule in various tissues. It has multiple features that may contribute to its cardiovascular protection. Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiological barriers. Additionally, this indoleamine also serves as a safe exogenous therapeutic agent. Increasing evidence has demonstrated the beneficial effects of melatonin in preventing and improving cardiovascular risk factors. Exogenous administration of melatonin, as a result of its antioxidant and anti-inflammatory properties, has been reported to decrease blood pressure, protect against atherosclerosis, attenuate molecular and cellular damage resulting from cardiac ischemia/reperfusion, and improve the prognosis of myocardial infarction and heart failure. This review aims to summarize the beneficial effects of melatonin against these conditions, the possible protective mechanisms of melatonin, and its potential clinical applicability in CVDs.

Sirtuin 2 Exerts Regulatory Functions on Radiation-Induced Myocardial Fibrosis in Mice by Mediating H3K27 Acetylation of Galectin-3 Promoter

Background

Sirtuin 2 (SIRT2) and galectin-3 have been shown to protect the heart against fibrosis. However, their impacts on radiation-induced myocardial fibrosis (RIMF) remain to be elucidated. To deepen this understanding, the current study sought to explore the effects of SIRT2 and galectin-3 on RIMF and the underlying mechanisms.

Methods

Galectin-3 knockout mice were obtained, and a radiation-induced heart damage (RIHD) mouse model was induced by local radiation exposure to the heart. Lentivirus transfection was then performed, and heart function, fibrosis of heart tissues, and levels of SIRT2, galectin-3, and fibrosis-related markers collagen type-I/-III and matrix metalloproteinase (MMP)2/MMP9 were respectively assessed by echocardiography, hematoxylin-eosin and Masson staining, reverse transcription-quantitative polymerase chain reaction, Western blot, and immunofluorescence staining. Additionally, Western blot and chromatin immunoprecipitation were used to test H3K27 acetylation levels and the binding of H3K27ac to galectin-3, respectively.

Results

After radiation exposure, heart tissues from the galectin-3 knockout mice had a smaller fibrotic area compared to normal mice, with reduced expression levels of collagen type-I/-III and MMP2/MMP9. SIRT2 was down-regulated and galectin-3 was up-regulated after RIHD treatment. The histone deacetylase inhibitor sirtinol promoted galectin-3 expression and H3K27 acetylation in a time-dependent manner, and increased H3K27ac enrichment in the galectin-3 promoter. Overexpression of SIRT2 down-regulated H3K27ac, collagen type-I/-III, and MMP2/MMP9 expression levels, and reduced the fibrotic area in mouse heart tissues. However, these effects were reversed by the additional overexpression of galectin-3.

Conclusions

SIRT2 facilitates deacetylation of H3K27 to inhibit galectin-3 transcription, thus ameliorating RIMF in mice.

NAD in pathological cardiac remodeling: Metabolic regulation and beyond

Nicotinamide adenine dinucleotide (NAD) coenzymes are carriers of high energy electrons in metabolism and also play critical roles in numerous signaling pathways. NAD metabolism is decreased in various cardiovascular diseases. Importantly, stimulation of NAD biosynthesis protects against heart disease under different pathological conditions. In this review, we describe pathways for both generation and catabolism of NAD coenzymes and the respective changes of these pathways in the heart under cardiac diseases, including pressure overload, myocardial infarction, cardiometabolic disease, cancer treatment cardiotoxicity, and heart failure. We next provide an update on the strategies and treatments to increase NAD levels, such as supplementation of NAD precursors, in the heart that prevent or reverse cardiomyopathy. We also introduce the approaches to manipulate NAD consumption enzymes to ameliorate cardiac disease. Finally, we discuss the mechanisms associated with improvements in cardiac function by NAD coenzymes, differentiating between mitochondria-dependent effects and those independent of mitochondrial metabolism.

Targeting HDAC6 to treat heart failure with preserved ejection fraction in mice

Heart failure with preserved ejection fraction (HFpEF) poses therapeutic challenges due to the limited treatment options. Building upon our previous research that demonstrates the efficacy of histone deacetylase 6 (HDAC6) inhibition in a genetic cardiomyopathy model, we investigate HDAC6's role in HFpEF due to their shared mechanisms of inflammation and metabolism. Here, we show that inhibiting HDAC6 with TYA-018 effectively reverses established heart failure and its associated symptoms in male HFpEF mouse models. Additionally, in male mice lacking Hdac6 gene, HFpEF progression is delayed and they are resistant to TYA-018's effects. The efficacy of TYA-018 is comparable to a sodium-glucose cotransporter 2 (SGLT2) inhibitor, and the combination shows enhanced effects. Mechanistically, TYA-018 restores gene expression related to hypertrophy, fibrosis, and mitochondrial energy production in HFpEF heart tissues. Furthermore, TYA-018 also inhibits activation of human cardiac fibroblasts and enhances mitochondrial respiratory capacity in cardiomyocytes. In this work, our findings show that HDAC6 impacts on heart pathophysiology and is a promising target for HFpEF treatment.

microRNA-143 targets SIRT2 to mediate the histone acetylation of PLAUR and modulates functions of astrocytes in spinal cord injury

This study aimed to explore effects of microRNA (miR)-143 on the proliferation, apoptosis, and cytokine secretion in astrocytes after spinal cord injury (SCI). After gain- and loss-of-function assays and transforming growth factor (TGF)-β stimulation in astrocytes, the cell viability, proliferation, and apoptosis were examined. The expression of miR-143, SIRT2, and PLAUR and levels of astrocyte-related glial fibrillary acidic protein (GFAP), Vimentin, chondroitin sulfate proteoglycan (CSPG), and connective tissue growth factor (CTGF) were also measured. The binding relationship between miR-143 and SIRT2 was assessed, as well as the correlation of PLAUR with SIRT2. In established SCI rat models, the locomotion function and astrocyte hyperplasia were detected. The TGF-β stimulation decreased miR-143 but increased SIRT2 expression in astrocytes. Mechanistically, miR-143 negatively targeted SIRT2 and SIRT2 down-regulation inhibited the H3K27 deacetylation of PLAUR promoter to increase PLAUR expression. miR-143 up-regulation inhibited TGF-β stimulated-proliferation, promoted cell apoptosis, and reduced GFAP, Vimentin, CSPG, and CTGF expression in astrocytes, which was counterweighed by SIRT2 overexpression. SIRT2 silencing reduced the proliferation and GFAP, Vimentin, CSPG, and CTGF expression while augmenting the apoptosis in TGF-β stimulated astrocytes, which was abrogated by PLAUR silencing. The injection of miR-143 agomir improved the locomotion function and reduced the astrocyte hyperplasia in SCI rats, which was reversed by silencing PLAUR. miR-143 targeted SIRT2 to affect PLAUR expression via the regulation of histone acetylation, which repressed the astrocyte activation in vivo and in vitro to improve the locomotion function in SCI rats.

The role of Sirtuin 2 in liver - An extensive and complex biological process

Liver disease has become one of the main causes of health issue worldwide. Sirtuin (Sirt) 2 is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, and is expressed in multiple organs including liver, which plays important and complex roles by interacting with various substrates. Physiologically, Sirt2 can improve metabolic homeostasis. Pathologically, Sirt2 can alleviate inflammation, endoplasmic reticulum (ER) stress, promote liver regeneration, maintain iron homeostasis, aggravate fibrogenesis and regulate oxidative stress in liver. In liver diseases, Sirt2 can mitigate fatty liver disease (FLD) including non-alcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD), but aggravate hepatitis B (HBV) and liver ischemia-reperfusion injury (LIRI). The role of Sirt2 in liver cancer and aging-related liver diseases, however, has not been fully elucidated. In this review, these biological processes regulated by Sirt2 in liver are summarized, which aims to update the function of Sirt2 in liver and to explore the potential role of Sirt2 as a therapeutic target for liver diseases.