SIRT1 inhibition promotes atherosclerosis through impaired autophagy

The role of sirtuins and uncoupling proteins on vascular aging: The Northern Manhattan Study experience

Aging affects all organs. Arteries, in particular, are among the most affected. Vascular aging (VA) is defined as age-associated changes in function and structure of vessels. Classical VA phenotypes are carotid intima-media thickness (IMT), carotid plaque (CP), and arterial stiffness (STIFF). Individuals have different predisposition to these VA phenotypes and their associated risk of cardiovascular events. Some develop an early vascular aging (EVA), and others are protected and identified as having supernormal vascular aging (SUPERNOVA). The mechanisms leading to these phenotypes are not well understood. In the Northern Manhattan Study (NOMAS), we found genetic variants in the 7 Sirtuins (SIRT) and 5 Uncoupling Proteins (UCP) to be differently associated with risk to developing VA phenotypes. In this article, we review the results of genetic-epidemiology studies to better understand which of the single nucleotide polymorphisms (SNPs) in SIRT and UCP are responsible for both EVA and SUPERNOVA.

Modulation of atherosclerosis-related signaling pathways by Chinese herbal extracts: Recent evidence and perspectives

Atherosclerotic cardiovascular disease remains a preeminent cause of morbidity and mortality globally. The onset of atherosclerosis underpins the emergence of ischemic cardiovascular diseases, including coronary heart disease (CHD). Its pathogenesis entails multiple factors such as inflammation, oxidative stress, apoptosis, vascular endothelial damage, foam cell formation, and platelet activation. Furthermore, it triggers the activation of diverse signaling pathways including Phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt), NF-E2-related factor 2/antioxidant response element (Nrf2/ARE), the Notch signaling pathway, peroxisome proliferator-activated receptor (PPAR), nucleotide oligo-structural domain-like receptor thermoprotein structural domain-associated protein 3 (NLRP3), silencing information regulator 2-associated enzyme 1 (Sirt1), nuclear transcription factor-κB (NF-κB), Circular RNA (Circ RNA), MicroRNA (mi RNA), Transforming growth factor-β (TGF-β), and Janus kinase-signal transducer and activator of transcription (JAK/STAT). Over recent decades, therapeutic approaches for atherosclerosis have been dominated by the utilization of high-intensity statins to reduce lipid levels, despite significant adverse effects. Consequently, there is a growing interest in the development of safer and more efficacious drugs and therapeutic modalities. Traditional Chinese medicine (TCM) offers a vital strategy for the prevention and treatment of cardiovascular diseases. Numerous studies have detailed the mechanisms through which TCM active ingredients modulate signaling molecules and influence the atherosclerotic process. This article reviews the signaling pathways implicated in the pathogenesis of atherosclerosis and the advancements in research on TCM extracts for prevention and treatment, drawing on original articles from various databases including Google Scholar, Medline, CNKI, Scopus, and Pubmed. The objective is to furnish a reference for the clinical management of cardiovascular diseases.

Therapy Combining Glucagon-Like Peptide-1 Receptor Agonist with Sodium-Glucose Cotransporter 2 Inhibitor Suppresses Atherosclerosis in Diabetic ApoE-Deficient Mice

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter 2 inhibitors (SGLT2i) have beneficial effects on cardiovascular disease in addition to their glucose-lowering effects. In this study, the effects of these drugs, when used individually or in combination, on cardiovascular atherosclerotic lesion development were compared in diabetic ApoE-deficient (ApoE KO) hyperlipidemic mice.

METHODS

ApoE-KO mice were treated with streptozotocin and nicotinamide, generating a type 2 diabetes model. The mice were randomly divided into four groups: vehicle-treated (untreated), liraglutide (LIRA), ipragliflozin (IPRA), and combination therapy (combo). These mice, as well as non-diabetic controls, were fed a high-fat diet. After 8 weeks of drug administration, the heart and aorta were removed and analyzed.

RESULTS

Atherosclerotic lesions evaluated by oil red O (ORO) staining were significantly larger in the untreated group (13.4±0.8% of the total aortic area) than in the non-diabetic controls (4.4±0.5%, p<0.01), while being reduced in the combo group (6.0±1.0%, p<0.01) as compared with the untreated group. The ORO stain-positive area in the LIRA and IPRA groups tended to be reduced but their differences were not statistically significant. Transcript levels of Mcp1 and Sirt1 were significantly reduced and increased, respectively, in the combo compared with the untreated group, while no significant changes were observed in the monotherapy groups.

CONCLUSIONS

The data suggest that combination therapy with liraglutide and ipragliflozin may be an efficient regimen for preventing the development of atherosclerosis in diabetic mice deficient in ApoE.

The anti-atherosclerotic effect of Paeonol against the lipid accumulation in macrophage-derived foam cells by inhibiting ferroptosis via the SIRT1/NRF2/GPX4 signaling pathway

Atherosclerosis (AS) is the underlying cause of many severe vascular diseases and is primarily characterized by abnormal lipid metabolism. Paeonol (Pae), a bioactive compound derived from Paeonia Suffruticosa Andr., is recognized for its significant role in reducing lipid accumulation. Our research objective is to explore the link between lipid buildup in foam cells originating from macrophages and the process of ferroptosis, and explore the effect and mechanism of Pae on inhibiting AS by regulating ferroptosis. In our animal model, ApoE-deficient mice, which were provided with a high-fat regimen to provoke atherosclerosis, were administered Pae. The treatment was benchmarked against simvastatin and ferrostatin-1. The results showed that Pae significantly reduced aortic ferroptosis and lipid accumulation in the mice. In vitro experiments further demonstrated that Pae could decrease lipid accumulation in foam cells induced by oxidized low-density lipoprotein (LDL) and challenged with the ferroptosis inducer erastin. Crucially, the protective effect of Pae against lipid accumulation was dependent on the SIRT1/NRF2/GPX4 pathway, as SIRT1 knockdown abolished this effect. Our findings suggest that Pae may offer a novel therapeutic approach for AS by inhibiting lipid accumulation through the suppression of ferroptosis, mediated by the SIRT1/NRF2/GPX4 pathway. Such knowledge has the potential to inform the creation of novel therapeutic strategies aimed at regulating ferroptosis within the context of atherosclerosis.

A novel circular RNA, circSQSTM1, protects the endothelial function in atherosclerosis

A novel circRNA named circSQSTM1 (hsa_circRNA_075320) was screened out in atorvastatin (ATV) stimulated endothelial cells (ECs) by our group. Considering the anti-atherosclerotic function of ATV, we hypothesized the circSQSTM1 could protect ECs functions in AS progression. The effects of circSQSTM1 on ECs inflammation, oxidative stress and autophagy were measured by qRT-PCR, Western blotting, monocyte-endothelial adhesion assay, dichloro-dihydro-fluorescein diacetate and mCherry-GFP-LC3 labeling. A luciferase reporter assay, RNA immunoprecipitation, MS2-tagging system and fluorescence in situ hybridization were performed to identify the biological functions of circSQSTM1. The partial left carotid artery ligation model and atherosclerosis model were established to analyze the effects of circSQSTM1 on atherosclerosis progression in vivo. Our results revealed that ATV induced the accumulation of circSQSTM1 in ECs via suppressing m6A modified degradation. In the cytoplasm, circSQSTM1 could relieve Sirt1 by competitively sponging miR-23b-3p. In the nucleus, circSQSTM1 directly interacts with eIF4A3 and promoting the efficient nuclear export of FOXO1 mRNA, which encodes FOXO1 transcription factor to directly activate Sirt1 promoter activity. Hence, circSQSTM1 reduced inflammation, inhibited oxidative stress and promoted autophagy by upregulating Sirt1 in ECs. Moreover, circSQSTM1 overexpression in ECs attenuated the progression of atherosclerosis in ApoE-/- mice. Taken together, the unique noncoding RNA known as circSQSTM1 took a protective role to the ECs in atherosclerosis.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

The role of the tryptophan-NAD + pathway in a mouse model of severe malnutrition induced liver dysfunction

Mortality in children with severe malnutrition is strongly related to signs of metabolic dysfunction, such as hypoglycemia. Lower circulating tryptophan levels in children with severe malnutrition suggest a possible disturbance in the tryptophan-nicotinamide adenine dinucleotide (TRP-NAD+) pathway and subsequently in NAD+  dependent metabolism regulator sirtuin1 (SIRT1). Here we show that severe malnutrition in weanling mice, induced by 2-weeks of low protein diet feeding from weaning, leads to an impaired TRP-NAD+  pathway with decreased NAD+ levels and affects hepatic mitochondrial turnover and function. We demonstrate that stimulating the TRP-NAD+  pathway with NAD+  precursors improves hepatic mitochondrial and overall metabolic function through SIRT1 modulation. Activating SIRT1 is sufficient to induce improvement in metabolic functions. Our findings indicate that modulating the TRP-NAD+  pathway can improve liver metabolic function in a mouse model of severe malnutrition. These results could lead to the development of new interventions for children with severe malnutrition.

The Value of SIRT1/FOXO1 Signaling Pathway in Early Detection of Cardiovascular Risk in Children with β-Thalassemia Major

Background: Atherosclerosis represents one of the major causes of morbidity in children with β-thalassemia major (β-TM). Aim: This study was designed to investigate SIRT1-FOXO1 signaling in β-TM children and their role in early detection of premature atherosclerosis. Methods: We equally subdivided 100 Egyptian children aged 6−14 years with β-TM according to carotid intima media thickness (CIMT) into 50 with CIMT < 0.5 mm and 50 with CIMT ≥ 0.5 mm, and 50 healthy children of matched age were included. They were subjected to evaluation of SIRT1, heat shock protein 72 (HSP72), and hepcidin levels via ELISA and forkhead box protein 1 (FOXO1) mRNA expression using real-time PCR in PBMCs; meanwhile, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase activities were evaluated spectrophotometrically. Results: Our results show significantly high values for CIMT, β-stiffness, atherogenic index of plasma (AIP), MDA, HSP72 and FOXO1, ferritin with significantly low hepcidin, SOD, catalase, and SIRT1 in β-TM as compared to controls with a more significant difference in β-TM with CIMT ≥ 0.5 mm than those with CIMT < 0.5 mm. A significant positive correlation between CIMT and MDA, HSP72, and FOXO1 gene expression was found, while a significant negative correlation with hepcidin, SOD, catalase, and SIRT1 was found. FOXO1 gene expression and HSP72 levels were the strongest independent determinants of CIMT. Conclusion: In β-TM, FOXO1 signaling is activated with low levels of SIRT1, and this is attributed to accelerated atherosclerosis in β-TM, which would be crucial in prediction of atherosclerosis.

Sirtuins in atherosclerosis: guardians of healthspan and therapeutic targets

Sirtuins are NAD⁺-dependent deacetylase and deacylase enzymes that control important cellular processes, including DNA damage repair, cellular metabolism, mitochondrial function and inflammation. Consequently, mammalian sirtuins are regarded as crucial regulators of cellular function and organism healthspan. Sirtuin activity and NAD⁺ levels decrease with age in many tissues, and reduced sirtuin expression is associated with several cardiovascular diseases. By contrast, increased sirtuin expression and activity slows disease progression and improves cardiovascular function in preclinical models and delays various features of cellular ageing. The potential cardiometabolic benefits of sirtuins have resulted in clinical trials with sirtuin-modulating agents; although expectations are high, these drugs have not yet been proven to improve healthspan. In this Review, we examine the role of sirtuins in atherosclerosis, summarize advances in the development of compounds that activate or inhibit sirtuin activity and critically evaluate the therapeutic potential of these agents.

A bibliometric analysis of autophagy in atherosclerosis from 2012 to 2021

Background: Regulation of autophagy affects the progression of atherosclerosis. In recent years, research on autophagy in atherosclerosis has been widely concerned. However, there is no bibliometric analysis in this field.

Objective: The purpose of this study was to explore the general situation, hot spots, and trends of the research in this field through bibliometric analysis.

Methods: Articles related to autophagy in atherosclerosis from 2012 to 2021 were retrieved from the Web of Science Core Collection. VOSviewer and CiteSpace were used for data analysis and visualization of countries, institutions, authors, keywords, journals, and citations.

Results: A total of 988 articles were obtained in the last 10 years. The number of publications and citations increased rapidly from 2012 to 2021, especially after 2019. The most productive countries, institutions, journals, and authors were the People’s Republic of China, Shandong University, Arteriosclerosis Thrombosis and Vascular Biology, and Wim Martinet, respectively. The primary keywords were “oxidative stress,” “apoptosis,” “activated protein kinase,” and “inflammation.” The burst detection analysis of keywords found that “SIRT1” and “long non-coding RNA” might be regarded as the focus of future research.

Conclusion: This is the first bibliometric analysis of autophagy in atherosclerosis, which reports the hot spots and emerging trends. The interaction between oxidative stress and autophagy, programmed cell death, and activated protein kinases are considered to be the current research priorities. Molecular mechanisms and therapeutic target for the intervention of atherosclerosis by regulating autophagy will become an emerging research direction.

HAND2-AS1 targeting miR-1208/SIRT1 axis alleviates foam cell formation in atherosclerosis

The abnormally expressed long non-coding RNAs (lncRNAs) exert an important part in the occurrence and development of cardiovascular disease, however, their roles in atherosclerosis (AS) remains unknown. This work focused on investigating the role of HAND2 Antisense RNA 1 (HAND2-AS1) and the related mechanism. As a result, SIRT1 and HAND2-AS1 expression significantly decreased in plasma from patients with atherosclerotic plaques and macrophages originating from THP-1 induced by ox-LDL. Lentivirus mediated HAND2-AS1 overexpression markedly inhibited lipid absorption and deposition within foam cells originating from THP-1 macrophages. HAND2-AS1 endogenously sponged miR-128 and suppressed its activity via sequence complementation. Furthermore, HAND2-AS1 enhanced the expression of SIRT1 via binding to miR-128, thereby promoting ABCA1/G1 expression. Altogether, HAND2-AS1 targeting miR-1208/SIRT1 axis alleviates the formation of foam cells within AS. Besides, HAND2-AS1 may be used to be the possible anti-AS therapeutic target.

Additive contribution of microRNA-34a/b/c to human arterial ageing and atherosclerosis

BACKGROUND AND AIMS

Preclinical data suggest that the ageing-induced miR-34a regulates vascular senescence. Herein we sought to assess whether the miR-34 family members miR-34a, miR-34b and miR-34c are involved in human arterial disease.

METHODS

Expression levels of miR-34a/b/c were quantified by TaqMan assay in peripheral blood mononuclear cells (PBMCs) derived from a consecutive cohort of 221 subjects who underwent cardiovascular risk assessment and thorough vascular examination for aortic stiffness and extent of arterial atherosclerosis.

RESULTS

High miR-34a was independently associated with the presence of CAD [OR (95%C.I.): 3.87 (1.56-9.56); p = 0.003] and high miR-34c with the number of diseased arterial beds [OR (95%C.I.): 1.88 (1.034-3.41); p = 0.038], while concurrent high expression of miR-34-a/c or all three miR-34a/b/c was associated with aortic stiffening (miR-34a/c: p = 0.022; miR-34a/b/c: p = 0.041) and with the extent of atherosclerosis [OR (95%C.I.) for number of coronary arteries [miR-34a/c: 3.29 (1.085-9.95); miR-34a/b/c: 6.06 (1.74-21.2)] and number of diseased arterial beds [miR-34a/c: 3.51 (1.45-8.52); miR-34a/b/c: 2.89 (1.05-7.92)] after controlling for possible confounders (p < 0.05 for all). Mechanistically, the increased levels of miR-34a or miR-34c were inversely associated with expression of SIRT1 or JAG1, NOTCH2, CTNNB1 and ATF1, respectively. The association of miR-34a/c or miR-34a/b/c with CAD was mainly mediated through SIRT1 and to a lesser extent through JAG1 as revealed by generalized structural equation modeling. Leukocyte-specific ablation of miR-34a/b/c ameliorates atherosclerotic plaque development and increases Sirt1 and Jag1 expression in an atherosclerosis mouse model confirming the human findings.

CONCLUSIONS

The present study reveals the clinical significance of the additive role of miR-34a/b/c in vascular ageing and atherosclerotic vascular disease.

Role of macrophage autophagy in atherosclerosis: modulation by bioactive compounds

Atherosclerosis is a chronic inflammatory disease associated with lipid metabolism disorder. Autophagy is a catabolic process and contributes to maintaining cellular homeostasis. Substantial evidence suggests that defective autophagy is implicated in several diseases, including atherosclerosis, while increased autophagy mitigates atherosclerosis development. Thus, understanding the mechanisms of autophagy regulation and its association with atherosclerosis is vital to develop new therapies against atherosclerosis. Dietary bioactive compounds are non-nutrient natural compounds that include phenolics, flavonoids, and carotenoids. Importantly, these bioactive compounds possess anti-inflammatory, antioxidant, and antibacterial properties that may alleviate various chronic diseases. Recently, examining the effects of bioactive compounds on autophagy activity in atherogenesis has drawn considerable attention. The current review discusses the role of macrophage autophagy in the development and progression of atherosclerosis. We also summarize our current knowledge of the therapeutic potential of bioactive compounds on atherosclerosis and autophagy.

Biochemical mechanism and biological effects of the inhibition of silent information regulator 1 (SIRT1) by EX-527 (SEN0014196 or selisistat)

The human sirtuin silent information regulator 1 (SIRT1) is a NAD⁺-dependent deacetylase enzyme. It deacetylates many protein substrates, including histones and transcription factors, thereby controlling many physiological and pathological processes. Several synthetic inhibitors and activators of SIRT1 have been developed, and some therapeutic applications have been explored. The indole EX-527 and its derivatives are among the most potent and selective SIRT1 inhibitors. EX-527 has been often used as a pharmacological tool to explore the effect of SIRT1 inhibition in various cell types. Its therapeutic potential has, therefore, been evaluated in animal models for several pathologies, including cancer. It has also been tested in phase II clinical trial for the treatment of Huntington’s disease (HD). In this review, we will provide an overview of the literature on EX-527, including its mechanism of inhibition and biological studies.

SIRT1 suppresses burn injury-induced inflammatory response through activating autophagy in RAW264.7 macrophages

The present study sought to investigate the association between silent information regulator 1 (SIRT1) and autophagy during systemic inflammatory response syndrome following burn injury. The experimental burn model in mice and macrophages were established. SIRT1 mRNA expression was quantified by quantitative real-time PCR. The protein levels of SIRT1 and the conversion of light chain 3 (LC3)-I to LC3-II were determined by western blot analysis. The formation of autophagosomes was assessed by green fluorescence protein-tagged LC3 fluorescence. The contents of inflammatory cytokines interleukin (IL)-1, IL-6, IL-10 and IL-18 were measured by ELISA. SIRT1 was highly expressed in burned tissues and RAW264.7 cells treated with serum obtained from mice with burn injuries. Moreover, SIRT1 overexpression augmented, whereas sirtinol, an inhibitor of SIRT1, attenuated burn injury-induced increasing number of autophagosomes and expression levels of LC3-II/LC3-I in RAW264.7 cells. Besides, sirtinol effectively prevented SIRT1-induced pro-inflammation during burn injury. Furthermore, autophagy inhibition by 3-methyladenine significantly attenuated SIRT1 overexpression-mediated pro-inflammatory cytokine production. SIRT1 abolished burn injury-induced inflammatory response by inducing autophagy.

Atorvastatin promotes bone formation in aged apoE-/- mice through the Sirt1-Runx2 axis

Background

Statins are the most widely used drugs in elderly patients; the most common clinical application of statins is in aged hyperlipemia patients. There are few studies on the effects and mechanisms of statins on bone in elderly mice with hyperlipemia. The study is to examine the effects of atorvastatin on bone phenotypes and metabolism in aged apolipoprotein E-deficient (apoE^–/–) mice, and the possible mechanisms involved in these changes.

Methods

Twenty-four 60-week-old apoE^–/– mice were randomly allocated to two groups. Twelve mice were orally gavaged with atorvastatin (10 mg/kg body weight/day) for 12 weeks; the others served as the control group. Bone mass and skeletal microarchitecture were determined using micro-CT. Bone metabolism was assessed by serum analyses, qRT-PCR, and Western blot. Bone marrow-derived mesenchymal stem cells (BMSCs) from apoE^–/– mice were differentiated into osteoblasts and treated with atorvastatin and silent information regulator 1 (Sirt1) inhibitor EX-527.

Results

The results showed that long-term administration of atorvastatin increases bone mass and improves bone microarchitecture in trabecular bone but not in cortical bone. Furthermore, the serum bone formation marker osteocalcin (OCN) was ameliorated by atorvastatin, whereas the bone resorption marker tartrate-resistant acid phosphatase 5b (Trap5b) did not appear obviously changes after the treatment of atorvastatin. The mRNA expression of Sirt1, runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and OCN in bone tissue were increased after atorvastatin administration. Western blot showed same trend in Sirt1 and Runx2. The in vitro study showed that when BMSCs from apoE^–/– mice were pretreated with EX527, the higher expression of Runx2, ALP, and OCN activated by atorvastatin decreased significantly or showed no difference compared with the control. The protein expression of Runx2 showed same trend.

Conclusions

Accordingly, the current study validates the hypothesis that atorvastatin can increase bone mass and promote osteogenesis in aged apoE^−/− mice by regulating the Sirt1–Runx2 axis.

Activation of SIRT1 promotes cartilage differentiation and reduces apoptosis of nucleus pulposus mesenchymal stem cells via the MCP1/CCR2 axis in subjects with intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a condition involving disruption of the bone tissue distribution. Nucleus pulposus mesenchymal stem cells (NPMSCs) and Sirtuin 1 (SIRT1) play important roles in bone diseases, therefore the aim of the present study was to evaluate the roles of SIRT1 and NPMSCs in IDD. First, NPMSCs were harvested from patients with IDD. Then, the NPMSCs were treated with a SIRT activator, and monocyte chemoattractant protein 1 (MCP1) and chemokine receptor 2 (CCR2) inhibitors. Indices related to NPMSC growth, proliferation, differentiation and apoptosis were measured. Subsequently, IDD rat models were established and were transfected with NPMSCs overexpressing SIRT1. NPMSC apoptosis and cartilage differentiation were detected in the rat IDD model. SIRT1 expression was found to be decreased, and the expression of MCP1 and CCR2 increased in NPMSCs of patients with IDD. The upregulation of SIRT1 and the downregulation of the MCP1/CCR2 axis promoted cartilage differentiation and reduced the number of apoptotic NPMSCs. Furthermore, MCP1 reversed the progression of the cartilage differentiation of NPMSCs and the inhibition of NPMSC apoptosis induced by SIRT1 overexpression. Moreover, the transplantation of rat NPMSCs overexpressing SIRT1 relieved IDD in rats. Therefore, SIRT1 overexpression improved cartilage differentiation and reduced the apoptosis of NPMSCs by inactivating the MCP1/CCR2 axis, thus attenuating IDD in rats.

SIRT1/2 orchestrate acquisition of DNA methylation and loss of histone H3 activating marks to prevent premature activation of inflammatory genes in macrophages

Sirtuins 1 and 2 (SIRT1/2) are two NAD-dependent deacetylases with major roles in inflammation. In addition to deacetylating histones and other proteins, SIRT1/2-mediated regulation is coupled with other epigenetic enzymes. Here, we investigate the links between SIRT1/2 activity and DNA methylation in macrophage differentiation due to their relevance in myeloid cells. SIRT1/2 display drastic upregulation during macrophage differentiation and their inhibition impacts the expression of many inflammation-related genes. In this context, SIRT1/2 inhibition abrogates DNA methylation gains, but does not affect demethylation. Inhibition of hypermethylation occurs at many inflammatory loci, which results in more drastic upregulation of their expression upon macrophage polarization following bacterial lipopolysaccharide (LPS) challenge. SIRT1/2-mediated gains of methylation concur with decreases in activating histone marks, and their inhibition revert these histone marks to resemble an open chromatin. Remarkably, specific inhibition of DNA methyltransferases is sufficient to upregulate inflammatory genes that are maintained in a silent state by SIRT1/2. Both SIRT1 and SIRT2 directly interact with DNMT3B, and their binding to proinflammatory genes is lost upon exposure to LPS or through pharmacological inhibition of their activity. In all, we describe a novel role for SIRT1/2 to restrict premature activation of proinflammatory genes.

The inhibitor of autophagy SBI-0206965 aggravates atherosclerosis through decreasing myeloid-derived suppressor cells

Atherosclerosis (AS) is currently the leading cause of mortality worldwide, with the development of new strategies to prevent the formation and rupture of atherosclerotic plaques being a paramount area of research. Amounting evidence suggests autophagy has an important role in the pathogenesis of AS and may be a potential therapeutic target. In this study, the effect of SBI-0206965(6965), a novel inhibitor of autophagy, was tested on the development of AS in apolipoprotein E deficient (ApoE^−/−) mice. Systemic application of 6965 was found to aggravate AS, with increased plaque size and decreased plaque stability in comparison with the control. Of note, it was observed that 6965 decreased the proportion of myeloid-derived suppressor cells (MDSCs). Further investigation demonstrated MDSCs markedly alleviated AS in ApoE^−/− mice; while 6965 reduced the viability and promoted apoptosis of MDSCs in vitro. This is the first study describing an association between autophagy and MDSCs in AS models, providing a novel mechanism to potentially target in the management of this condition.

Depletion of CPEB1 protects against oxidized LDL-induced endothelial apoptosis and inflammation though SIRT1/LOX-1 signalling pathway

Atherosclerosis (AS) is a chronic inflammatory disease that results from Oxidized low-density lipoprotein (Ox-LDL) induced endothelial dysfunction. Cytoplasmic polyadenylation element binding protein 1 (CPEB1) is closely related to the development of epithelial cells, but the role of CPEB1 in AS remains unknown. The RNA and protein levels of CPEB1 expression are increased by Ox-LDL exposure, which is abrogated by c-Jun amino-terminal kinase (JNK) inhibitor SP600125. CPEB1 small interfering RNA (siRNA) suppressed the oxidative stress, inflammation, and apoptosis. Furthermore, CPEB1 siRNA enhanced the sirtuin 1 (SIRT1) transcription levels in Ox-LDL-treated HUVECs. Co-Immunoprecipitation (Co-IP) assay showed that CPEB1 siRNA declined the ubiquitination of SIRT1, and SIRT1 siRNA enhanced the Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), which were decreased by CPEB1 siRNA. In addition, LOX-1 and SIRT1 attenuated the protection of SIRT1 siRNA on Ox-LDL-induced oxidative stress. Therefore, our study revealed that CPEB1 depletion might play an anti-inflammatory and antiapoptotic role in Ox-LDL-induced apoptosis and inflammation though SIRT1/LOX-1 signalling pathway.

Effect of Autophagy Regulated by Sirt1/FoxO1 Pathway on the Release of Factors Promoting Thrombosis from Vascular Endothelial Cells

Factors promoting thrombosis such as von Willebrand factor (vWF) and P-selectin are essential for the development of atherosclerosis (AS) and arterial thrombosis. The processing, maturation and release of vWF are regulated by autophagy of vascular endothelial cells. The Sirt1/FoxO1 pathway is an important pathway to regulate autophagy of endothelial cells, therefore the Sirt1/FoxO1 pathway may be an important target for the prevention of thrombosis. We investigated the role of ox-LDL in the release of vWF and P-selectin and the expression of Sirt1 and FoxO1 by Western Blot, Flow Cytometry, ELISA, and tandem fluorescent mRFP-GFP-LC3. We found that vWF and P-selectin secretion increased and Sirt1/FoxO1 pathway was depressed in human umbilical vein endothelial cells (HUVEC) when treated with ox-LDL. Moreover, the expression of autophagy-related protein LC3-II/I and p62 increased. Then, we explored the relationship between autophagy regulated by the Sirt1/FoxO1 pathway and the secretion of vWF and P-selectin. We found that Sirt1/FoxO1, activated by the Sirt1 activators resveratrol (RSV) and SRT1720, decreased the secretion of vWF and P-selectin, which can be abolished by the autophagy inhibitor 3-MA. The expression of Rab7 increased when Sirt1/FoxO1 pathway was activated, and the accumulation of p62 was decreased. Autophagy flux was inhibited by ox-LDL and Sirt1/FoxO1 pathway might enhance autophagy flux through the promotion of the Rab7 expression. Taken together, our data suggest that by enhancing autophagy flux and decreasing the release of vWF and P-selectin, the Sirt1/FoxO1 pathway may be a promising target to prevent AS and arterial thrombosis.

MicroRNA‑217 is involved in the progression of atherosclerosis through regulating inflammatory responses by targeting sirtuin 1

Atherosclerosis is a chronic inflammatory disease, and it is a global clinical problem. The development of new and effective therapeutic targets for atherosclerosis is necessary. A number of microRNAs (miRNAs) have been demonstrated to serve a crucial role in atherosclerosis. However, the role of miRNA (miR)-217 in atherosclerosis remains unclear. Therefore, the aim of the present study was to investigate the role and mechanism of miR-217 in atherosclerosis. The level of miR-217 was detected in the blood of patients with atherosclerosis using reverse transcription-quantitative PCR. THP-1 acute monocytic leukemia cells were treated with oxidized low-density lipoprotein (ox-LDL) to develop an atherosclerotic cell model of macrophages. The relationship between miR-217 and sirtuin 1 (SIRT1) was determined by TargetScan and dual luciferase reporter assay. Cell apoptosis was measured by flow cytometry. Production of pro-inflammatory factors and triglyceride (TG) and total cholesterol (TC) levels were also determined. The results demonstrated that miR-217 was significantly upregulated in atherosclerosis. SIRT1 was demonstrated to be a direct target of miR-217 and was downregulated in atherosclerosis. Downregulation of miR-217 significantly inhibited ox-LDL-induced TG and TC level increase, cell apoptosis and the upregulation of the pro-inflammatory factors tumor necrosis factor α, interleukin (IL)-6 and IL-1β. Additionally, the SIRT1/AMP-activated protein kinase α/NF-κB pathway was at least partially involved in modulating the effects of miR-217 inhibition on THP-1 cells treated with ox-LDL. In addition, the effects of miR-217 downregulation on ox-LDL-treated THP-1 cells were eliminated by SIRT1 silencing. In conclusion, the results of the present study indicated that miR-217 downregulation may relieve atherosclerosis through the inhibition of macrophage apoptosis and inflammatory response by targeting SIRT1.

Salidroside protects against ox-LDL-induced endothelial injury by enhancing autophagy mediated by SIRT1-FoxO1 pathway

Background

Atherosclerosis is a condition with the vascular accumulation of lipid plaques, and its main major contributing factor is endothelial injury induced by oxidized low-density lipoprotein (ox-LDL). Salidroside (SAL) is the primary active ingredient of Rhodiola rosea, and exhibits antioxidant properties on endothelial cells and alleviates atherosclerosis. However, the effect of SAL on autophagy in ox-LDL-induced vascular endothelial injury remains unclear. Here, we investigated the effect and underlying mechanisms of SAL on autophagy in human umbilical vein endothelial cells (HUVECs).

Methods

HUVECs were incubated with ox-LDL to induce in vitro atherosclerosis model. The cell viability and injury were evaluated by cell counting kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release assay. The oxidative stress was evaluated by NADPH oxidase, malondialdehyde (MDA) and superoxide dismutase (SOD) activities. Immunofluorescence was performed to detect autophagy using LC3β antibody. Quantitative real-time PCR (qRT-PCR) and western blot were performed to measure the mRNA expressions of SIRT1 and Forkhead box O1 (FOXO1). Nicotinamide (NAM) and AS1842856 were used to inhibit activities of SIRT1 and FOXO1, respectively.

Results

Exposure of HUVECs to ox-LDL (100 μg/mL) reduced cell viability, increased cellular MDA, and reduced SOD in a concentration-dependent manner. The pretreatment with SAL (20, 50 and 100 μM) significantly enhanced the cell viability and decreased LDH release in HUVECs exposed to ox-LDL (100 μg/mL). ox-LDL induced autophagy in HUVECs, which was further enhanced by pretreatment with SAL. However, SAL attenuated increase in oxidative stress in HUVECs induced by ox-LDL. ox-LDL reduced mRNA and protein expressions of SIRT1 and FOXO1, which could be reversed by SAL. The protective, anti-oxidative and pro-autophagic effects of SAL could be obviously abolished by cotreatment with SIRT1 inhibitor or FOXO1 inhibitor.

Conclusion

Salidroside shows protective effect on endothelial cell induced by ox-LDL, and the mechanisms might be related to autophagy induction via increasing SIRT1 and FoxO1 expressions.

Targeting epigenetics and non-coding RNAs in atherosclerosis: from mechanisms to therapeutics

Atherosclerosis, the principal cause of cardiovascular death worldwide, is a pathological disease characterized by fibro-proliferation, chronic inflammation, lipid accumulation, and immune disorder in the vessel wall. As the atheromatous plaques develop into advanced stage, the vulnerable plaques are prone to rupture, which causes acute cardiovascular events, including ischemic stroke and myocardial infarction. Emerging evidence has suggested that atherosclerosis is also an epigenetic disease with the interplay of multiple epigenetic mechanisms. The epigenetic basis of atherosclerosis has transformed our knowledge of epigenetics from an important biological phenomenon to a burgeoning field in cardiovascular research. Here, we provide a systematic and up-to-date overview of the current knowledge of three distinct but interrelated epigenetic processes (including DNA methylation, histone methylation/acetylation, and non-coding RNAs), in atherosclerotic plaque development and instability. Mechanistic and conceptual advances in understanding the biological roles of various epigenetic modifiers in regulating gene expression and functions of endothelial cells (vascular homeostasis, leukocyte adhesion, endothelial-mesenchymal transition, angiogenesis, and mechanotransduction), smooth muscle cells (proliferation, migration, inflammation, hypertrophy, and phenotypic switch), and macrophages (differentiation, inflammation, foam cell formation, and polarization) are discussed. The inherently dynamic nature and reversibility of epigenetic regulation, enables the possibility of epigenetic therapy by targeting epigenetic "writers", "readers", and "erasers". Several Food Drug Administration-approved small-molecule epigenetic drugs show promise in pre-clinical studies for the treatment of atherosclerosis. Finally, we discuss potential therapeutic implications and challenges for future research involving cardiovascular epigenetics, with an aim to provide a translational perspective for identifying novel biomarkers of atherosclerosis, and transforming precision cardiovascular research and disease therapy in modern era of epigenetics.

Ginkgo Biloba Leaf Extract Attenuates Atherosclerosis in Streptozotocin-Induced Diabetic ApoE-/- Mice by Inhibiting Endoplasmic Reticulum Stress via Restoration of Autophagy through the mTOR Signaling Pathway

Background

There is a crosstalk between endoplasmic reticulum stress (ERS) and autophagy, and autophagy could attenuate endoplasmic reticulum stress-mediated apoptosis. Ginkgo biloba leaf extract (GBE) exerts vascular protection functions. The purpose of the present study is to investigate the role of autophagy in diabetic atherosclerosis (AS) and the effect of GBE on autophagy and ERS.

Methods

Network pharmacology was utilized to predict the targets and pathways of the active chemical compounds of Gingko biloba leaf to attenuate AS. ApoE^−/− mice were rendered diabetic by intraperitoneal ingestion with streptozotocin combined with a high-fat diet. The diabetic mice were divided into five groups: model group, atorvastatin group, rapamycin group, and low- and high-dose GBE groups. Serum and tissue markers of autophagy or ERS markers, including the protein expression, were examined.

Results

The mammalian target of rapamycin (mTOR) and NF-κB signaling pathways were targeted by the active chemical compounds of GBE to attenuate AS predicted by network pharmacology. GBE reduced the plaque area/lumen area and the plaque lipid deposition area/intimal area and inhibited the expressions of CD68, MMP2, and MMP9. Rapamycin and GBE inhibited the expression of mTOR and SQSTM1/p62 which increased in the aorta of diabetic mice. In addition, GBE reduced the expression of ERS markers in diabetic mice. GBE reduced the serum lipid metabolism levels, blood glucose, and inflammatory cytokines.

Conclusion

Impaired autophagy and overactive endoplasmic reticulum stress contributed to diabetic atherosclerosis. mTOR inhibitor rapamycin and GBE attenuated diabetic atherosclerosis by inhibiting ERS via restoration of autophagy through inhibition of mTOR.

Protective effects of ex-527 on cerebral ischemia-reperfusion injury through necroptosis signaling pathway attenuation

Necroptosis, a novel type of programmed cell death, is involved in ischemia-reperfusion-induced brain injury. Sirtuin 1 (Sirt1), as a well-known member of histone deacetylase class III, plays pivotal roles in inflammation, metabolism, and neuron loss in cerebral ischemia. We explored the relationship between Sirt1 and the necroptosis signaling pathway and its downstream events by administration of ex-527, as a selective and potent inhibitor of Sirt1, and necrostatin-1 (nec-1), as a necroptosis inhibitor, in an animal model of focal cerebral ischemia. Our data showed different patterns of sirt1 and necroptosis critical regulators, including receptor-interacting protein kinase 3 and mixed lineage kinase domain-like protein gene expressions in the prefrontal cortex and the hippocampus after ischemia-reperfusion. We found that ex-527 microinjection reduces the infarction volume of ischemic brains and improves the survival rate, but not stroke-associated neurological deficits. Additionally, treatment with ex-527 effectively abolished the elevation of the critical regulators of necroptosis, whereas necroptosis inhibition through nec-1 microinjection did not influence Sirt1 expression levels. Our data also demonstrated that the ex-527 relieves ischemia-induced perturbation of necroptosis-associated metabolic enzymes activity in downstream. This study provides a new approach to the possible neuroprotective potential of ex-527 orchestrated by necroptosis pathway inhibition to alleviate ischemia-reperfusion brain injury.

Atherosclerotic plaque instability in carotid arteries: miR-200c as a promising biomarker

Early recognition of vulnerable carotid plaques could help in identifying patients at high stroke risk, who may benefit from earlier revascularisation. Nowadays, different biomarkers of plaque instability have been unravelled, among these miRNAs are promising tools for the diagnosis and treatment of atherosclerosis. Inflammation, reactive oxygen species (ROS) and endothelial dysfunction play a key role in unstable plaques genesis. We showed that miR-200c induces endothelial dysfunction, ROS production and a positive mechanism among miR-200c and miR-33a/b, two miRNAs involved in atherosclerosis progression. The goal of the present study was to determine whether miR-200c could be an atherosclerosis biomarker. Carotid plaques of patients that underwent carotid endarterectomy (CEA) were assayed for miR-200c expression. miR-200c was up-regulated in carotid plaques (n=22) and its expression was higher in unstable (n=12) compared with stable (n=10) plaques. miR-200c positively correlated with instability biomarkers (i.e. monocyte chemoattractant protein-1, cicloxigenase-2 (COX2), interleukin 6 (IL6), metalloproteinase (MMP) 1 (MMP1), 9 (MMP9)) and miR-33a/b. Moreover, miR-200c negatively correlated with stability biomarkers (i.e. zinc finger E-box binding homoeobox 1 (ZEB1), endothelial nitric oxide (NO) synthase (eNOS), forkhead boxO1 (FOXO1) and Sirtuin1 (SIRT1)) (stable plaques = 15, unstable plaques = 15). Circulating miR-200c was up-regulated before CEA in 24 patients, correlated with miR-33a/b and decreased 1 day after CEA. Interestingly, 1 month after CEA, circulating miR-200c is low in patients with stable plaques (n=11) and increased to control levels, in patients with unstable plaques (n=13). Further studies are needed to establish whether miR-200c represents a circulating biomarker of plaque instability. Our results show that miR-200c is an atherosclerotic plaque progression biomarker and suggest that it may be clinically useful to identify patients at high embolic risk.

Whey Protein Attenuates Angiotensin II-Primed Premature Senescence of Vascular Smooth Muscle Cells through Upregulation of SIRT1

Whey protein, a by-product of milk curdling, exhibits diverse biological activities and is used as a dietary supplement. However, its effects on stress-induced vascular aging have not yet been elucidated. In this study, we found that whey protein significantly inhibited the Ang II-primed premature senescence of vascular smooth muscle cells (VSMCs). In addition, we observed a marked dose- and time-dependent increase in SIRT1 promoter activity and mRNA in VSMCs exposed to whey protein, accompanied by elevated SIRT1 protein expression. Ang II-mediated repression of SIRT1 level was dose-dependently reversed in VSMCs treated with whey protein, suggesting that SIRT1 is involved in preventing senescence in response to this treatment. Furthermore, resveratrol, a well-defined activator of SIRT1, potentiated the effects of whey protein on Ang II-primed premature senescence, whereas sirtinol, an inhibitor of SIRT1, exerted the opposite. Taken together, these results indicated that whey protein-mediated upregulation of SIRT1 exerts an anti-senescence effect, and can thus ameliorate Ang IIinduced vascular aging as a dietary supplement.

Cordycepin stimulates autophagy in macrophages and prevents atherosclerotic plaque formation in ApoE-/- mice

Autophagy in macrophages plays a key role in the pathogenesis and progression of atherosclerosis and has become a potential therapeutic target. Here we show that cordycepin (Cpn), a natural derivative of adenosine, markedly reduced atherosclerotic plaque and ameliorated associated symptoms such as dyslipidemia, hyperglycemia and inflammation in ApoE^-/- mice. Supplementation of Cpn dose-dependently inhibited oxLDL-elicited foam cell formation and modulated intracellular cholesterol homeostasis by inhibiting cholesterol uptake and promoting cholesterol efflux in RAW264.7 macrophages. Notably, Cpn exhibited significant stimulating effect on macrophage autophagy, as estimated by western blotting, immunofluorescent staining and autophagic vacuoles observation by transmission electron microscopy. The inhibitive effects of Cpn on foam cell formation were dramatically deteriorated in the presence of various autophagy inhibitors, suggesting that autophagy participate, at least in part, in the atheroprotective role of Cpn. Further investigations using different autophagy inhibitors and specific siRNAs for AMP-activated protein kinase (AMPK) gamma1 subunit indicated that Cpn may stimulate macrophage autophagy through AMPK-mTOR pathway. Together, our results demonstrated Cpn as a potential therapeutic agent for the prevention and treatment of atherosclerosis, and the autophagic activity presents a novel mechanism for Cpn-mediated atheroprotection.

The SIRT1 inhibitor EX-527 suppresses mTOR activation and alleviates acute lung injury in mice with endotoxiemia

It is generally regarded that Sirtuin 1 (SIRT1), a longevity factor in mammals, acts as a negative regulator of inflammation. However, recent studies also found that SIRT1 might be a detrimental factor under certain inflammatory circumstance. In this study, the potential pathophysiological roles and the underlying mechanisms of SIRT1 in a mouse model with endotoxemia-associated acute lung injury were investigated. The results indicated that treatment with the selective SIRT1 inhibitor EX-527 suppressed LPS-induced elevation of TNF-α and IL-6 in plasma. Treatment with EX-527 attenuated LPS-induced histological abnormalities in lung tissue, which was accompanied with decreased myeloperoxidase level and suppressed induction of tissue factor and plasminogen activator inhibitor-1. Treatment with EX-527 also suppressed LPS-induced phosphorylation of eukaryotic translation initiation factor-binding protein 1 (4E-BP1). Co-administration of a mammalian target of rapamycin (mTOR) activator 3-benzyl-5-[(2-nitrophenoxy) methyl]-dihydrofuran-2 (3H)-one (3BDO) abolished the inhibitory effects of EX-527 on 4E-BP1 phosphorylation. Meanwhile, the inhibitory effects of EX-527 on IL-6 induction and the beneficial effects of EX-527 on lung injury were partially reversed by 3BDO. This study suggests that selective inhibition of SIRT1 by EX-527 might alleviate endotoxemia-associated acute lung injury partially via suppression of mTOR, which implies that SIRT1 selective inhibitors might have potential value for the pharmacological intervention of inflammatory lung injury.