SIRT6-mediated transcriptional suppression of MALAT1 is a key mechanism for endothelial to mesenchymal transition

Endothelial microRNAs and long noncoding RNAs in cardiovascular ageing

Atherosclerosis and numerous other cardiovascular diseases develop in an age-dependent manner. The endothelial cells that line the vessel walls play an important role in the development of atherosclerosis. Non-coding RNA like microRNAs and long non-coding RNAs are known to play an important role in endothelial function and are implicated in the disease progression. Here, we summarize several microRNAs and long non-coding RNAs that are known to have an altered expression with endothelial aging and discuss their role in endothelial cell function and senescence. These processes contribute to aging-induced atherosclerosis development and by targeting the non-coding RNAs controlling endothelial cell function and senescence, atherosclerosis can potentially be attenuated.

Histone modification of endothelial-mesenchymal transition in cardiovascular diseases

Endothelial-mesenchymal transition (EndMT) is a differentiation process in which endothelial cells lose their own characteristics and acquire mesenchymal-like characteristics, which contributes to the formation and development of atherosclerotic plaques. Until now, there is still a lack of effective measures to treat atherosclerosis (AS), so there is an urgent need to understand the underlying mechanisms of AS. In addition, although various studies have shown that EndMT is involved in the pathological stages of cardiovascular diseases, such as myocardial fibrosis, myocardial hypertrophy, and hypertension, the specific molecular mechanisms driving EndMT are still in the exploratory stage. In this review, we review the role of histone modifications (methylation, demethylation and acetylation, deacetylation) on EndMT in cardiovascular disease, aiming to target histone-modifying enzymes to guide cardiovascular disease therapy.

Role of the cGAS-STING Pathway in Aging-related Endothelial Dysfunction

Endothelial dysfunction develops gradually with age, and is the foundation of many age-related diseases in the elderly. The purpose of this study was to investigate the role of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in aging-related endothelial dysfunction. Endothelial functional parameters and biochemical indices of vascular function were examined in 2-, 6-, 12- and 24-month-old mice. Then, 6-month-old mice were administered RU.521, a specific inhibitor of cGAS, for 6 months, and endothelial functional parameters and biochemical indices of vascular function were re-examined. An in vitro model of cell senescence was established by treating human aortic endothelial cells (HAECs) with D-Galactose (D-GAL). Using inhibitors or siRNA interference, cGAS and STING were suppressed or silenced in senescent HAECs, and changes in the expression of eNOS, the senescence markers, p53, p21 and p16, components of the cGAS-STING pathway and Senescence-Associated β-galactosidase (SA-β-gal) staining were examined. Finally, cGAS, STING and p-IRF3 levels were measured in aorta tissue sections from eight patients. A decline in endothelial function, up-regulation of p53, p21 and p16 expression, and activation of the cGAS-STING pathway were observed in aging mice. Inhibition of cGAS was found to improve endothelial function and reverse the increased expression of aging markers. Our in vitro data demonstrated that D-GAL induced a decrease in eNOS expression and cell senescence, which could be partly reversed by cGAS inhibitor, STING inhibitor, siRNA-cGAS and siRNA-STING treatment. Higher expression levels of cGAS, STING and p-IRF3 were observed in aged human aortic intima tissue compared to young aortic intima tissue. Our study demonstrated that activation of the cGAS-STING pathway played a vital role in aging-related endothelial dysfunction. Thus, the cGAS-STING pathway may be a potential target for the prevention of cardiovascular diseases in the elderly.

Potential epigenetic molecular regulatory networks in ocular neovascularization

Neovascularization is one of the many manifestations of ocular diseases, including corneal injury and vascular diseases of the retina and choroid. Although anti-VEGF drugs have been used to effectively treat neovascularization, long-term use of anti-angiogenic factors can cause a variety of neurological and developmental side effects. As a result, better drugs to treat ocular neovascularization are urgently required. There is mounting evidence that epigenetic regulation is important in ocular neovascularization. DNA methylation and histone modification, non-coding RNA, and mRNA modification are all examples of epigenetic mechanisms. In order to shed new light on epigenetic therapeutics in ocular neovascularization, this review focuses on recent advances in the epigenetic control of ocular neovascularization as well as discusses these new mechanisms.

Breaking the aging epigenetic barrier

Aging is an inexorable event occurring universally for all organisms characterized by the progressive loss of cell function. However, less is known about the key events occurring inside the nucleus in the process of aging. The advent of chromosome capture techniques and extensive modern sequencing technologies have illuminated a rather dynamic structure of chromatin inside the nucleus. As cells advance along their life cycle, chromatin condensation states alter which leads to a different epigenetic landscape, correlated with modified gene expression. The exact factors mediating these changes in the chromatin structure and function remain elusive in the context of aging cells. The accumulation of DNA damage, reactive oxygen species and loss of genomic integrity as cells cease to divide can contribute to a tumor stimulating environment. In this review, we focus on genomic and epigenomic changes occurring in an aged cell which can contribute to age-related tumor formation.

Research progress of endothelial-mesenchymal transition in diabetic kidney disease

Renal fibrosis is an important pathological feature of diabetic kidney disease (DKD), manifested as tubular interstitial fibrosis, tubular atrophy, glomerulosclerosis and damage to the normal structure of the kidney. Renal fibrosis can eventually develop into renal failure. A better understanding of renal fibrosis in DKD is needed due to clinical limitations of current anti‐fibrotic drugs in terms of effectiveness, cost‐effectiveness and side effects. Fibrosis is characterized by local excessive deposition of extracellular matrix, which is derived from activated myofibroblasts to increase its production or specific tissue inhibitors of metalloproteinases to reduce its degradation. In recent years, endothelial‐mesenchymal transition (EndMT) has gradually integrated into the pathogenesis of fibrosis. In animal models of diabetic kidney disease, it has been found that EndMT is involved in the formation of renal fibrosis and multiple signalling pathways such as TGF‐β signalling pathway, Wnt signalling pathway and non‐coding RNA network participate in the regulation of EndMT during fibrosis. Here, we mainly review EndMT regulation and targeted therapy of renal fibrosis in DKD.

SIRT6 inhibits endothelial-to-mesenchymal transition through attenuating the vascular endothelial inflammatory response

Endothelial-to-mesenchymal transition (EndMT) is a process of transdifferentiation in which endothelial cells gradually adopt the phenotypic characteristics of mesenchymal cells. Emerging studies demonstrate the importance of EndMT in endothelial dysfunction during inflammation. Sirtuin 6 (SIRT6), a member of the mammalian NAD⁺-dependent deacetylase sirtuin family, plays a critical role in cardiovascular diseases by regulating the inflammatory response. However, little is known about the effect of SIRT6 on EndMT during vascular inflammation. Therefore, we aimed to investigate the effect of SIRT6 on EndMT in endothelium-specific SIRT6 knockout (ecSIRT6^-/-) mice and human umbilical vein endothelial cells (HUVECs) stimulated with inflammatory cytokines. First, we found that TNF-α and IL-1β co-treatment induced EndMT and down-regulated SIRT6 expression in HUVECs. Adenovirus-mediated SIRT6 overexpression suppressed inflammation-induced EndMT in HUVECs. In contrast, SIRT6 knockdown further promoted EndMT. Our findings also revealed that SIRT6 attenuated the inflammatory response of HUVECs. Additionally, vascular inflammation was induced by carotid artery ligation in ecSIRT6^-/- mice. Results showed that the intima of ligated carotid arteries in ecSIRT6^-/- mice was significantly thickened compared to that in ecSIRT6^+/+ ligated mice. Moreover, endothelium-specific SIRT6 knockout promoted EndMT and increased the expression of proinflammatory cytokines in the carotid arteries of mice. These results suggest that SIRT6 inhibits EndMT through attenuating the vascular endothelial inflammatory response. These findings may have significance for reducing the occurrence of EndMT and ameliorating certain aspects of vascular inflammation.

SIRT6 Through the Brain Evolution, Development, and Aging

During an organism's lifespan, two main phenomena are critical for the organism's survival. These are (1) a proper embryonic development, which permits the new organism to function with high fitness, grow and reproduce, and (2) the aging process, which will progressively undermine its competence and fitness for survival, leading to its death. Interestingly these processes present various similarities at the molecular level. Notably, as organisms became more complex, regulation of these processes became coordinated by the brain, and failure in brain activity is detrimental in both development and aging. One of the critical processes regulating brain health is the capacity to keep its genomic integrity and epigenetic regulation-deficiency in DNA repair results in neurodevelopmental and neurodegenerative diseases. As the brain becomes more complex, this effect becomes more evident. In this perspective, we will analyze how the brain evolved and became critical for human survival and the role Sirt6 plays in brain health. Sirt6 belongs to the Sirtuin family of histone deacetylases that control several cellular processes; among them, Sirt6 has been associated with the proper embryonic development and is associated with the aging process. In humans, Sirt6 has a pivotal role during brain aging, and its loss of function is correlated with the appearance of neurodegenerative diseases such as Alzheimer's disease. However, Sirt6 roles during brain development and aging, especially the last one, are not observed in all species. It appears that during the brain organ evolution, Sirt6 has gained more relevance as the brain becomes bigger and more complex, observing the most detrimental effect in the brains of Homo sapiens. In this perspective, we part from the evolution of the brain in metazoans, the biological similarities between brain development and aging, and the relevant functions of Sirt6 in these similar phenomena to conclude with the evidence suggesting a more relevant role of Sirt6 gained in the brain evolution.

Endothelial Dysfunction in Atherosclerotic Cardiovascular Diseases and Beyond: From Mechanism to Pharmacotherapies

The endothelium, a cellular monolayer lining the blood vessel wall, plays a critical role in maintaining multiorgan health and homeostasis. Endothelial functions in health include dynamic maintenance of vascular tone, angiogenesis, hemostasis, and the provision of an antioxidant, anti-inflammatory, and antithrombotic interface. Dysfunction of the vascular endothelium presents with impaired endothelium-dependent vasodilation, heightened oxidative stress, chronic inflammation, leukocyte adhesion and hyperpermeability, and endothelial cell senescence. Recent studies have implicated altered endothelial cell metabolism and endothelial-to-mesenchymal transition as new features of endothelial dysfunction. Endothelial dysfunction is regarded as a hallmark of many diverse human panvascular diseases, including atherosclerosis, hypertension, and diabetes. Endothelial dysfunction has also been implicated in severe coronavirus disease 2019. Many clinically used pharmacotherapies, ranging from traditional lipid-lowering drugs, antihypertensive drugs, and antidiabetic drugs to proprotein convertase subtilisin/kexin type 9 inhibitors and interleukin 1β monoclonal antibodies, counter endothelial dysfunction as part of their clinical benefits. The regulation of endothelial dysfunction by noncoding RNAs has provided novel insights into these newly described regulators of endothelial dysfunction, thus yielding potential new therapeutic approaches. Altogether, a better understanding of the versatile (dys)functions of endothelial cells will not only deepen our comprehension of human diseases but also accelerate effective therapeutic drug discovery. In this review, we provide a timely overview of the multiple layers of endothelial function, describe the consequences and mechanisms of endothelial dysfunction, and identify pathways to effective targeted therapies. SIGNIFICANCE STATEMENT: The endothelium was initially considered to be a semipermeable biomechanical barrier and gatekeeper of vascular health. In recent decades, a deepened understanding of the biological functions of the endothelium has led to its recognition as a ubiquitous tissue regulating vascular tone, cell behavior, innate immunity, cell-cell interactions, and cell metabolism in the vessel wall. Endothelial dysfunction is the hallmark of cardiovascular, metabolic, and emerging infectious diseases. Pharmacotherapies targeting endothelial dysfunction have potential for treatment of cardiovascular and many other diseases.

Inhibition of miR-122 reduced atherosclerotic lesion formation by regulating NPAS3-mediated endothelial to mesenchymal transition

AIMS

Endothelial to mesenchymal transition (EndMT) is closely related to atherosclerosis. Herein, we aim to determine whether miR-122 is involved in EndMT and the underlying mechanism in atherosclerosis.

MAIN METHODS

qRT-PCR was performed to detect miR-122 expression in ApoE^-/- mice and cellular EndMT model induced by H₂O₂. MiR-122 expression in vivo was modulated by lenti-virus injection and by genetic manipulation. Hematoxylin and eosin (HE) and Oil-red O staining were used to observe the plaque size and lipid accumulation in the aortic roots. F4/80 staining, elastin staining, and masson staining were used to observe the components of atherosclerotic lesions. MiR-122 expression in endothelial cells was modulated by transfection of miR-122 mimic and inhibitor. Western blotting and co-localization of endothelial markers (VE-cadherin, CD31) and mesenchymal markers (Vimentin, α-SMA) were carried out to determine EndMT.

KEY FINDINGS

MiR-122 was upregulated in the aortic intima and serum of ApoE^-/- mice induced by HFD and in cellular EndMT model. Inhibition of miR-122 repressed the atherosclerotic plaque progression and vulnerable plaque formation in ApoE^-/- mice. In vitro, endothelial cells acquired a spindle-shaped morphology accompanying decrease of the endothelial markers (VE-cadherin, CD31) and increase of the mesenchymal markers (Vimentin, α-SMA) in the presence of H₂O₂, which was inhibited by miR-122 inhibitor. Furthermore, NPAS3 functions as a target of miR-122, and NPAS3 silencing abolished the anti-EndMT effect of miR-122 inhibitor.

SIGNIFICANCE

Inhibition of miR-122 prevents atherosclerosis and regulates NPAS3-mediated EndMT, suggesting that miR-122 may be a novel target in the treatment of EndMT-associated diseases including atherosclerosis.

Protein Coding and Long Noncoding RNA (lncRNA) Transcriptional Landscape in SARS-CoV-2 Infected Bronchial Epithelial Cells Highlight a Role for Interferon and Inflammatory Response

The global spread of COVID-19, caused by pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) underscores the need for an imminent response from medical research communities to better understand this rapidly spreading infection. Employing multiple bioinformatics and computational pipelines on transcriptome data from primary normal human bronchial epithelial cells (NHBE) during SARS-CoV-2 infection revealed activation of several mechanistic networks, including those involved in immunoglobulin G (IgG) and interferon lambda (IFNL) in host cells. Induction of acute inflammatory response and activation of tumor necrosis factor (TNF) was prominent in SARS-CoV-2 infected NHBE cells. Additionally, disease and functional analysis employing ingenuity pathway analysis (IPA) revealed activation of functional categories related to cell death, while those associated with viral infection and replication were suppressed. Several interferon (IFN) responsive gene targets (IRF9, IFIT1, IFIT2, IFIT3, IFITM1, MX1, OAS2, OAS3, IFI44 and IFI44L) were highly upregulated in SARS-CoV-2 infected NBHE cell, implying activation of antiviral IFN innate response. Gene ontology and functional annotation of differently expressed genes in patient lung tissues with COVID-19 revealed activation of antiviral response as the hallmark. Mechanistic network analysis in IPA identified 14 common activated, and 9 common suppressed networks in patient tissue, as well as in the NHBE cell model, suggesting a plausible role for these upstream regulator networks in the pathogenesis of COVID-19. Our data revealed expression of several viral proteins in vitro and in patient-derived tissue, while several host-derived long noncoding RNAs (lncRNAs) were identified. Our data highlights activation of IFN response as the main hallmark associated with SARS-CoV-2 infection in vitro and in human, and identified several differentially expressed lncRNAs during the course of infection, which could serve as disease biomarkers, while their precise role in the host response to SARS-CoV-2 remains to be investigated.

Sirt6 deficiency aggravates angiotensin II-induced cholesterol accumulation and injury in podocytes

Disturbed renal lipid metabolism, especially cholesterol dysregulation plays a crucial role in the pathogenesis of chronic kidney disease (CKD). We recently reported that angiotensin (Ang) II could induce cholesterol accumulation and injury in podocytes. However, the underlying mechanisms for these alterations remain unknown. Methods: Bioinformatics analysis of renal biopsy specimens from patients with hypertensive nephropathy (HN) suggests the involvement of Sirtuin 6 (Sirt6) in Ang II-induced dysregulation of glomerular cholesterol. Using a podocyte-specific Sirt6 knockout mouse model, the effects of Sirt6 on Ang II-induced cholesterol accumulation in podocytes and the therapeutic efficacies of cholesterol-lowering agents were evaluated. Results: Cholesterol accumulation was detected in the podocytes of Ang II-infused mice, whereas selective deletion of Sirt6 in podocytes not only increased cholesterol accumulation in these cells but also exacerbated Ang II-induced kidney injury. Deletion of Sirt6 also attenuated the protective effect of cyclodextrin (CD) on Ang II-induced urinary albumin excretion, glomerulosclerosis and podocyte injury. In addition, we demonstrated that Sirt6 affected cholesterol efflux in podocytes by regulating the expression of ATP-binding cassette transporter G1 (ABCG1). Conclusions: These findings provide evidence that Sirt6 is a potential target for renin-angiotensin system (RAS)-associated podocyte injury and provide a rationale for the application of cholesterol-lowering agents in patients with CKD.

Immunomodulatory and Antioxidant Activities of a Polysaccharide from Ligustrum vicaryi L. Fruit

Ligustrum vicaryi L. is a hybrid of Ligustrum ovalifolium Hassk. var. aureo-marginatum and Ligustrum vulgale L., belonging to the Oleaceae family. It is often used as an ornamental shrub due to its golden leaves. However, its medical value is yet to be discovered. Recently, plant polysaccharides have attracted comprehensive attention owing to their biological properties, including immunomodulatory and antioxidant activities. This study aimed to extract, purify, and characterize the polysaccharide from the Ligustrum vicaryi L. fruit and investigate its immunomodulatory and antioxidant activities. The Ligustrum vicaryi L. fruit polysaccharide (LVFP) was obtained by ultrasonic extraction, ethanol precipitation, macroporous resin separation, and dialysis bag purification. The physicochemical properties of the LVFP were elucidated using Fourier-transform infrared spectrometry, high-performance ion chromatography, and high-performance gel filtration chromatography. The results indicated that the LVFP consisted of rhamnose, arabinose, galactose, and glucose in a ratio of 1.79 : 7.55 : 4.58 : 1.54, and its molecular weight was 88,949 Da. The immunomodulatory and antioxidant activities of the LVFP were investigated using a cyclophosphamide- (Cy-) induced immunosuppressed mouse model. The results demonstrated that the LVFP significantly increased spleen and thymus indexes, enhanced the phagocytic function of neutrophils, activated B and T lymphocytes, and upregulated serum levels of IL-10 and TNF-α. Moreover, we observed that the LVFP relieved Cy-induced liver damage by increasing superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) levels. These results suggested that the LVFP has the immunomodulatory and antioxidant activities, therefore laying a foundation for the application of the LVFP in the pharmaceutical and functional food industries.

Endothelial to mesenchymal transition contributes to nicotine-induced atherosclerosis

Rationale: Nicotine exposure via cigarette smoking is strongly associated with atherosclerosis. However, the underlying mechanisms remain poorly understood. The current study aimed to identify whether endothelial to mesenchymal transition (EndMT) contributes to nicotine-induced atherosclerosis. Methods: ApoE-/- mice were administered nicotine in their drinking water for 12 weeks. The effects of nicotine on EndMT were determined by immunostaining on aortic root and RNA analysis in aortic intima. In vitro nicotine-treated cell model was established on human aortic endothelial cells (HAECs). The effects of nicotine on the expression of EndMT-related markers, ERK1/2 and Snail were quantified by real-time PCR, western blot and immunofluorescent staining. Results: Nicotine treatment resulted in larger atherosclerotic plaques in ApoE-/- mice. The vascular endothelial cells from nicotine-treated mice showed mesenchymal phenotype, indicating EndMT. Moreover, nicotine-induced EndMT process was accompanied by cytoskeleton reorganization and impaired barrier function. The α7 nicotine acetylcholine receptor (α7nAChR) was highly expressed in HAECs and its antagonist could effectively relieve nicotine-induced EndMT and atherosclerotic lesions in mice. Further experiments revealed that ERK1/2 signaling was activated by nicotine, which led to the upregulation of Snail. Blocking ERK1/2 with inhibitor or silencing Snail by small interfering RNA efficiently preserved endothelial phenotype upon nicotine stimulation. Conclusion: Our study provides evidence that EndMT contributes to the pro-atherosclerotic property of nicotine. Nicotine induces EndMT through α7nAChR-ERK1/2-Snail signaling in endothelial cells. EndMT may be a therapeutic target for smoking-related endothelial dysfunction and cardiovascular disease.

Sirt6-Mediated Endothelial-to-Mesenchymal Transition Contributes Toward Diabetic Cardiomyopathy via the Notch1 Signaling Pathway

BACKGROUND

Endothelial-to-mesenchymal transition (EndMT) is an important source of myofibroblasts that directly affects cardiac function in diabetic cardiomyopathy (DCM) via an unknown underlying mechanism. Sirt6 is a member of the Sirtuin family of NAD(+)-dependent enzymes that plays an important role in glucose and fatty acid metabolism. In this study, we investigated whether Sirt6 participates in EndMT during the development of T2DM and the possible underlying regulatory mechanisms.

METHODS

Endothelium-specific Sirt6 knockout (Sirt6-KO^EC) mice (C57BL/6 genetic background) were generated using the classic Cre/loxp gene recombination system. T2DM was induced in eight-week-old male mice by feeding with a high-fat diet for three weeks followed by i.p. injection with 30 mg/kg of streptozotocin. The weight, lipids profiles, insulin, food intake and water intake of experimental animals were measured on a weekly basis. Cardiac microvascular endothelial cells (CMECs) were obtained from adult male mice; the isolated cells were cultured with high glucose (HG; 33 mmol/L) and palmitic acid (PA; 500 μmol/L) in DMEM for 24 h, or with normal glucose (NG; 5 mmol/L) as the control.

RESULTS

Sirt6 expression is significantly downregulated in CMECs treated with HG+PA. Additionally, Sirt6-KO^EC was found to worsen DCM, as indicated by aggravated perivascular fibrosis, cardiomyocyte hypertrophy, and decreased cardiac function. In vitro, Sirt6 knockdown exacerbated the proliferation, and migration of CMECs exposed to HG+PA. Mechanistically, Sirt6 knockdown significantly enhanced Notch1 activation in CMECs treated with HG+PA, whereas Notch1 adenoviral interference significantly blunted the effects of Sirt6 knockdown on CMECs.

CONCLUSION

This study is the first to demonstrate that Sirt6 participates in EndMT via the Notch1 signaling pathway in CMECs stimulated with HG+PA. Therefore, the findings of this study suggest that Sirt6 could provide a potential treatment strategy for DCM.

Metoprolol protects against myocardial infarction by inhibiting miR-1 expression in rats

OBJECTIVES

Metoprolol is regarded as a first-line medicine for the treatment of myocardial infarction (MI). However, the underlying mechanisms remain largely unknown. This study aimed to investigate the involvement of miR-1 in the pharmacological function of metoprolol.

METHODS

In vivo MI model was established by left anterior descending coronary artery (LAD) ligation. The effects of metoprolol on infarct size and cardiac dysfunction were determined by triphenyltetrazolium chloride staining and cardiac echocardiography, respectively. In vitro oxidative stress cardiomyocyte model was established by H₂ O₂ treatment. The effect of metoprolol on the expression of miR-1 and connexin43 (Cx43) was quantified by real-time PCR and western blot, respectively. The intercellular communication was evaluated by lucifer yellow dye diffusion.

KEY FINDINGS

Left anterior descending ligation-induced MI injury was markedly attenuated by metoprolol as shown by reduced infarct size and better cardiac function. Metoprolol reversed the up-regulation of miR-1 and down-regulation of Cx43 in MI heart. Moreover, in H₂ O₂ -stimulated cardiomyocytes, overexpression of miR-1 abolished the effects of metoprolol on Cx43 up-regulation and increased intercellular communication, indicating that miR-1 may be a necessary mediator for the cardiac protective function of metoprolol.

CONCLUSIONS

Metoprolol relieves MI injury via suppression miR-1, thus increasing its target protein Cx43 and improving intercellular communication.