AMP-Activated Protein Kinase and Sirtuin 1 Coregulation of Cortactin Contributes to Endothelial Function

A molecular and computational study of galbanic acid as a regulator of Sirtuin1 pathway in inhibiting lipid accumulation in HepG2 cells

INTRODUCTION

Sirtuin1 (SIRT1) plays a crucial role in the pathophysiology of non-alcoholic fatty liver disease. We investigated the mechanistic role of galbanic acid (Gal) as a regulator of SIRT1 in silico and in vitro.

METHODS

HepG2 cells were treated with Gal in the presence or absence of EX-527, a SIRT1-specific inhibitor, for 24 h. Sirtuin1 gene and protein expression were measured by RT-PCR and Western blotting, respectively. It has been docked to the allosteric reign of SIRT1 (PDB ID: 4ZZJ) to study the effect of Gal on SIRT1, and then the protein and complex molecular dynamic (MD) simulations had been studied in 100 ns.

RESULTS

The semi-quantitative results of Oil red (p < .03) and TG level (p < .009) showed a significant reduction in lipid accumulation by treatment with Gal. Also, a significant increase was observed in the gene and protein expression of SIRT1 (p < .05). MD studies have shown that the average root mean square deviation (RMSD) was about 0.51 Å for protein structure and 0.66 Å for the complex. The average of radius of gyration (Rg) is 2.33 and 2.32 Å for protein and complex, respectively, and the pattern of root mean square fluctuation (RMSF) was almost similar.

CONCLUSION

Computational studies show that Gal can be a great candidate to use as a SIRT1 ligand because it does not interfere with the structure of the protein, and other experimental studies showed that Gal treatment with SIRT1 inhibitor increases fat accumulation in HepG2 cells.

Translationally controlled tumor protein interacts with TaCIPK23 to positively regulate wheat resistance to Puccinia triticina

Hypersensitive response-programmed cell death (HR-PCD) regulated by Ca2+ signal is considered the major regulator of resistance against Puccinia triticina (Pt.) infection in wheat. In this study, the bread wheat variety Thatcher and its near-isogenic line with the leaf rust resistance locus Lr26 were infected with the Pt. race 260 to obtain the compatible and incompatible combinations, respectively. The expression of translationally controlled tumor protein (TaTCTP) was upregulated upon infection with Pt., through a Ca2+-dependent mechanism in the incompatible combination. The knockdown of TaTCTP markedly increased the area of dying cell and the number of Pt. haustorial mother cells (HMCs) at the infection sites, whereas plants overexpressing the gene exhibited enhanced resistance. The interaction between TaTCTP and calcineurin B-like protein-interacting protein kinase 23 (TaCIPK23) was also investigated, and the interaction was found occurred in the endoplasmic reticulum. TaCIPK23 phosphorylated TaTCTP in vitro. The expression of a phospho-mimic TaTCTP mutant in Nicotiana benthamiana promoted HR-like cell death. Silencing TaCIPK23 or TaCIPK23/TaTCTP co-silencing resulted in the same results as silencing TaTCTP. This suggested that TaTCTP is a novel phosphorylation target of TaCIPK23, and both participate in the resistance of wheat to Pt. in the same pathway.

Shear Stress-Induced AMP-Activated Protein Kinase Modulation in Endothelial Cells: Its Role in Metabolic Adaptions and Cardiovascular Disease

Endothelial cells (ECs) line the inner surface of all blood vessels and form a barrier that facilitates the controlled transfer of nutrients and oxygen from the circulatory system to surrounding tissues. Exposed to both laminar and turbulent blood flow, ECs are continuously subject to differential mechanical stimulation. It has been well established that the shear stress associated with laminar flow (LF) is atheroprotective, while shear stress in areas with turbulent flow (TF) correlates with EC dysfunction. Moreover, ECs show metabolic adaptions to physiological changes, such as metabolic shifts from quiescence to a proliferative state during angiogenesis. The AMP-activated protein kinase (AMPK) is at the center of these phenomena. AMPK has a central role as a metabolic sensor in several cell types. Moreover, in ECs, AMPK is mechanosensitive, linking mechanosensation with metabolic adaptions. Finally, recent studies indicate that AMPK dysregulation is at the center of cardiovascular disease (CVD) and that pharmacological targeting of AMPK is a promising and novel strategy to treat CVDs such as atherosclerosis or ischemic injury. In this review, we summarize the current knowledge relevant to this topic, with a focus on shear stress-induced AMPK modulation and its consequences for vascular health and disease.

AMPKα2 controls the anti-atherosclerotic effects of fish oils by modulating the SUMOylation of GPR120

Consuming fish oils (FO) is linked to reduced risk of cardiovascular disease in certain populations. However, FO failed to exhibit therapeutic effects in some patients with cardiovascular disease. This study aimed to determine the possible reasons for the inconsistent effects of FO. AMP-activated protein kinase (AMPK) α2 is an important energy metabolic sensor, which was reported to involve in FO mediated regulation of lipid and glucose metabolism. In an in vivo study, FO administration significantly reduced the aortic lesions and inflammation in the Ldlr^-/- mouse model of atherosclerosis, but not in Ldlr^-/-/Prkaa2^-/-and Ldlr^-/-/Prkaa2^-/-Sm22Cre mice. Mechanistically, inactivation of AMPKα2 increased the SUMOylation of the fatty acid receptor GPR120 to block FO-induced internalization and binding to β-arrestin. In contrast, activation of AMPKα2 can phosphorylate the C-MYC at Serine 67 to inhibit its trans-localization into the nuclei and transcription of SUMO-conjugating E2 enzyme UBC9 and SUMO2/3 in vascular smooth muscle cells (VSMCs), which result in GPR120 SUMOylation. In human arteries, AMPKα2 levels were inversely correlated with UBC9 expression. In a cohort of patients with atherosclerosis, FO concentrations did not correlate with atherosclerotic severity, however, in a subgroup analysis a negative correlation between FO concentrations and atherosclerotic severity was found in patients with higher AMPKα2 levels. These data indicate that AMPKα2 is required for the anti-inflammatory and anti-atherosclerotic effects of FO.

Endothelium-Derived Relaxing Factors and Endothelial Function: A Systematic Review

BACKGROUND

The endothelium plays a pivotal role in homeostatic mechanisms. It specifically modulates vascular tone by releasing vasodilatory mediators, which act on the vascular smooth muscle. Large amounts of work have been dedicated towards identifying mediators of vasodilation and vasoconstriction alongside the deleterious effects of reactive oxygen species on the endothelium. We conducted a systematic review to study the role of the factors released by the endothelium and the effects on the vessels alongside its role in atherosclerosis.

METHODS

A search was conducted with appropriate search terms. Specific attention was offered to the effects of emerging modulators of endothelial functions focusing the analysis on studies that investigated the role of reactive oxygen species (ROS), perivascular adipose tissue, shear stress, AMP-activated protein kinase, potassium channels, bone morphogenic protein 4, and P2Y2 receptor.

RESULTS

530 citations were reviewed, with 35 studies included in the final systematic review. The endpoints were evaluated in these studies which offered an extensive discussion on emerging modulators of endothelial functions. Specific factors such as reactive oxygen species had deleterious effects, especially in the obese and elderly. Another important finding included the shear stress-induced endothelial nitric oxide (NO), which may delay development of atherosclerosis. Perivascular Adipose Tissue (PVAT) also contributes to reparative measures against atherosclerosis, although this may turn pathological in obese subjects. Some of these factors may be targets for pharmaceutical agents in the near future.

CONCLUSION

The complex role and function of the endothelium is vital for regular homeostasis. Dysregulation may drive atherogenesis; thus, efforts should be placed at considering therapeutic options by targeting some of the factors noted.

New Insight in HDACs: Potential Therapeutic Targets for the Treatment of Atherosclerosis

Atherosclerosis (AS) features include progressive hardening and reduced elasticity of arteries. AS is the leading cause of morbidity and mortality. An increasing amount of evidence showed that epigenetic modifications on genes serve are a main cause of several diseases, including AS. Histone deacetylases (HDACs) promote the deacetylation at lysine residues, thereby condensing the chromatin structures and further inhibiting the transcription of downstream genes. HDACs widely affect various physiological and pathological processes through transcriptional regulation or deacetylation of other non-histone proteins. In recent years, the role of HDACs in vascular systems has been revealed, and their effects on atherosclerosis have been widely reported. In this review, we discuss the members of HDACs in vascular systems, determine the diverse roles of HDACs in AS, and reveal the effects of HDAC inhibitors on AS progression. We provide new insights into the potential of HDAC inhibitors as drugs for AS treatment.

FAIMS Enhances the Detection of PTM Crosstalk Sites

Protein post-translational modifications (PTMs) enable cells to rapidly change in response to biological stimuli. With hundreds of different PTMs, understanding these control mechanisms is complex. To date, efforts have focused on investigating the effect of a single PTM on protein function. Yet, many proteins contain multiple PTMs. Moreover, one PTM can alter the prevalence of another, a phenomenon termed PTM crosstalk. Understanding PTM crosstalk is critical; however, its detection is challenging since PTMs occur substoichiometrically. Here, we develop an enrichment-free, label-free proteomics method that utilizes high-field asymmetric ion mobility spectrometry (FAIMS) to enhance the detection of PTM crosstalk. We show that by searching for multiple combinations of dynamic PTMs on peptide sequences, a 6-fold increase in candidate PTM crosstalk sites is identified compared with that of standard liquid chromatography-tandem mass spectrometry (LC-MS/MS) workflows. Additionally, by cycling through FAIMS compensation voltages within a single LC-FAIMS-MS/MS run, we show that our LC-FAIMS-MS/MS workflow can increase multi-PTM-containing peptide identifications without additional increases in run times. With 159 novel candidate crosstalk sites identified, we envisage LC-FAIMS-MS/MS to play an important role in expanding the repertoire of multi-PTM identifications. Moreover, it is only by detecting PTM crosstalk that we can "see" the full picture of how proteins are regulated.

Endothelial Dysfunction in Hypertension: Current Concepts and Clinical Implications

Endothelium plays a fundamental role in the cardiovascular system, forming an interface between blood and adjacent tissues by regulating the vascular tone through the synthesis of nitric oxide, prostaglandins and other relaxing factors. Endothelial dysfunction is characterized by vasoconstriction, cell proliferation and shifting toward a proinflammatory and prothrombic state. In hypertension endothelial dysfunction may be involved in the initiation and development of vascular inflammation, vascular remodeling, and atherosclerosis and is independently associated with increased cardiovascular risk. Different conditions such as impaired vascular shear stress, inflammation and oxidative stress, activation of the renin angiotensin system have been described as important pathophysiological mechanisms involved in the development of endothelial dysfunction. The release of extracellular vesicles by neighboring cells in the vascular wall has emerged as an important regulator of endothelial function and with potential antihypertensive properties and beneficial effects by counteracting the hypertension mediated organ damage. Furthermore, macrovesicles are emerging as an innovative therapeutic approach for vascular protection, allowing the delivery of bioactive molecules, such as miRNA and drugs interacting with the renin angiotensin system. In this review we summarize the available evidence about the pathophysiological implications of endothelial dysfunction in cardiovascular diseases, focusing on hypertension and its sequelae, and the potential innovative therapeutic strategies targeting the endothelium with the aim to improve vascular function and remodeling.

Sirtuin1 in vascular endothelial function, an overview

Sirtuin1 is a nutrient-sensitive class III histone deacetylase which is a well-known regulator of organismal lifespan. It has been extensively studied for its role in metabolic regulation as well. Along with its involvement in ageing and metabolism, Sirtuin1 directly deacetylates many critical proteins controlling cardiovascular pathophysiology. Studies using conditional expression and deletion of Sirtuin1 have revealed that it functions in a highly tissue/organ-specific manner. In the vasculature, Sirtuin1 controls endothelial homoeostasis by governing the expression of inflammatory mediators, oxidants and essential transcription factors. Adding to this complexity, Sirtuin1 expression and/or function is also governed by some of these target proteins. Therefore, the importance of better understanding the organ and tissue specificity of Sirtuin1 is highly desirable. Considering the huge volume of research done in this field, this review focuses on Sirtuin1 targets regulating vascular endothelial function. Here, we summarize the discovery of Sirtuin1 as a transcription controller and the further identification of direct target proteins involved in the vascular physiology. Overall, this review presents a holistic picture of the complex cross-talk involved in the molecular regulation of vascular physiology by Sirtuin1.

Role of SIRT1/AMPK signaling in the proliferation, migration and invasion of renal cell carcinoma cells

Renal cell carcinoma (RCC) is a lethal urologic tumor commonly seen in men that best responds to partial nephrectomy. An enhanced understanding of the molecular pathogenesis of RCC can broaden treatment options and tumor prevention strategies. Sirtuin 1 (SIRT1) is a NAD+‑dependent deacetylase that regulates several bioactive substances, and the present study aimed to identify the role of SIRT1/AMP‑activated protein kinase (AMPK) signaling in RCC progression. SIRT1 expression was detected in 100 patients with RCC using tissue microarray immunohistochemistry. SIRT1‑knockdown and overexpression were performed via RNA interference and plasmid transfection. Inhibition of AMPK was used for the phenotypic rescue assays to verify whether AMPK was a downstream target of SIRT1. Reverse transcription‑quantitative PCR was performed to verify transfection efficiency. Transwell, MTT and flow cytometry apoptosis assays were performed to evaluate the migration, invasion, proliferation and early apoptosis level of RCC cells. SIRT1 and AMPK protein expression in human RCC tissues and cell lines (786‑O and ACHN) was detected using western blotting and immunofluorescence staining. The current results, combined with data from The Cancer Genome Atlas database, revealed that SIRT1 expression in RCC tissues was downregulated compared with in adjacent normal tissues. Additionally, high SIRT1 expression was associated with an improved prognosis in patients with RCC. Overexpression of SIRT1 inhibited the proliferation, migration and invasion of RCC cell lines and induced apoptosis, while inhibition of SIRT1 expression had the opposite effects. Further experiments indicated that SIRT1 may serve an anticancer role by upregulating the expression levels of downstream AMPK, thus revealing a potential therapeutic target for RCC.

[Angiotensin Ⅱ inhibits AMPK/SIRT1 pathway by inducing oxidative stress in RAW264.7 macrophages]

OBJECTIVE

To investigate the mechanism by which angiotensin Ⅱ-induced oxidative stress response inhibits AMPK/ SIRT1 signaling in RAW264.7 macrophages.

OBJECTIVE

RAW264.7 cells were treated with 0.5, 1, 3, 10, or 20 μmol/L angiotensin Ⅱ for 24 h, and the changes in the expressions of AMPK, p-AMPK, and SIRT1 proteins were detected using Western blotting. The intracellular ROS release level was measured and the levels of SOD and MDA were detected. The effects of angiotensin Ⅱ type 1 receptor (AT1R) gene silencing on the cell response to angiotensin Ⅱ treatment were examined by detecting the changes in AMPK, p-AMPK and SIRT1 protein levels. The effects of a ROS inhibitor on cellular AMPK and SIRT1 were also examined.

OBJECTIVE

Angiotensin Ⅱ stimulation at 20 μmol/L significantly inhibited the phosphorylation of AMPK protein and increased cellular ROS release (P < 0.05). Treatment with 0.5-10 μmol/L angiotensin Ⅱ did not cause significant changes in SOD activity or MDA expression, but angiotensin Ⅱ at the dose of 20 μmol/L significantly inhibited SOD activity in the cells (P < 0.05). In the macrophages with AT1R gene silencing, treatment with angiotensin Ⅱ did not obviously inhibit AMPK phosphorylation or down- regulate SIRT1 expression. In cells treated with the ROS inhibitor, angiotensin Ⅱ failed to lower the level of AMPK phosphorylation or the expression of SIRT1.

OBJECTIVE

Angiotensin Ⅱ induces oxidative stress to cause disturbance of AMPK/ SIRT1 signaling pathway in macrophages.

Atorvastatin and pravastatin stimulate nitric oxide and reactive oxygen species generation, affect mitochondrial network architecture and elevate nicotinamide N-methyltransferase level in endothelial cells

Statins belong to the most often prescribed medications, which efficiently normalise hyperlipidaemia and prevent cardiovascular complications in obese and diabetic patients. However, beside expected therapeutic results based on the inhibition of 3-hydroxyl-3-methylglutaryl-CoA reductase, these drugs exert multiple side effects of poorly understood characteristic. In this study, side effects of pravastatin and atorvastatin on EA.hy926 endothelial cell line were investigated. It was found that both statins activate proinflammatory response, elevate nitric oxide and reactive oxygen species (ROS) generation and stimulate antioxidative response in these cells. Moreover, only slight stimulation of the mitochondrial biogenesis and significant changes in the mitochondrial network organisation have been noted. Although biochemical bases behind these effects are not clear, they may partially be explained as an elevation of AMP-activated protein kinase (AMPK) activity and an increased activating phosphorylation of sirtuin 1 (Sirt1), which were observed in statins-treated cells. In addition, both statins increased nicotinamide N-methyltransferase (NNMT) protein level that may explain a reduced fraction of methylated histone H3. Interestingly, a substantial reduction of the total level of histone H3 in cells treated with pravastatin but not atorvastatin was also observed. These results indicate a potential additional biochemical target for statins related to reduced histone H3 methylation due to increased NNMT protein level. Thus, NNMT may directly modify gene activity.

SIRT1 Activation by Natural Phytochemicals: An Overview

Sirtuins are class III histone deacetylases, whose enzymatic activity is dependent on NAD⁺ as a cofactor. Sirtuins are reported to modulate numerous activities by controlling gene expression, DNA repair, metabolism, oxidative stress response, mitochondrial function, and biogenesis. Deregulation of their expression and/or action may lead to tissue-specific degenerative events involved in the development of several human pathologies, including cancer, neurodegeneration, and cardiovascular disease. The most studied member of this class of enzymes is sirtuin 1 (SIRT1), whose expression is associated with increasing insulin sensitivity. SIRT1 has been implicated in both tumorigenic and anticancer processes, and is reported to regulate essential metabolic pathways, suggesting that its activation might be beneficial against disorders of the metabolism. Via regulation of p53 deacetylation and modulation of autophagy, SIRT1 is implicated in cellular response to caloric restriction and lifespan extension. In recent years, scientific interest focusing on the identification of SIRT1 modulators has led to the discovery of novel small molecules targeting SIRT1 activity. This review will examine compounds of natural origin recently found to upregulate SIRT1 activity, such as polyphenolic products in fruits, vegetables, and plants including resveratrol, fisetin, quercetin, and curcumin. We will also discuss the potential therapeutic effects of these natural compounds in the prevention and treatment of human disorders, with particular emphasis on their metabolic impact.

Colchicine Alleviates Cholesterol Crystal-Induced Endothelial Cell Pyroptosis through Activating AMPK/SIRT1 Pathway

Cholesterol crystal- (CC-) induced endothelial cell inflammation and pyroptosis play an important role in the development of cardiovascular diseases, especially in atherosclerosis (AS). Increasing evidence suggests that cholesterol crystals are known to be a pivotal pathological marker of atherosclerotic plaque vulnerability. As a classical nonspecific anti-inflammatory drug, colchicine has been widely used in the treatment of acute gout. However, whether colchicine could alleviate CC-induced endothelial cell injury and the related mechanisms remains to be addressed. In this study, the protective effect of colchicine on human umbilical vein endothelial cells (HUVECs) was confirmed. Our results revealed that after cotreatment with colchicine and cholesterol crystals in endothelial cells, the uptake of cholesterol crystals was significantly decreased, the cell viability was obviously increased, and the release of lactate dehydrogenase (LDH) and the number of pyroptotic cells decreased significantly; then, the expression of NLRP3 inflammasome-related proteins and various inflammatory factors was also visibly suppressed; moreover, as a potent activator of NLRP3 inflammasome, the intracellular ROS level was clearly reduced, while mitochondrial membrane potential improved significantly. In addition, the expression levels of AMP-dependent kinase (AMPK) pathway-related proteins as well as various antioxidant enzymes were elevated notably in varying degrees. However, the above effects of colchicine were completely offset by the treatment of siRNA targeting AMPKα and Sirtuin1 (SIRT1). Therefore, we conclude that colchicine plays a crucial role in alleviating the intracellular inflammatory response and NLRP3 inflammation activation, attenuating the levels of cellular oxidative stress and pyroptosis in endothelial cells via regulating AMPK/SIRT1 signaling, which may be a concrete mechanism for the secondary prevention of cardiovascular diseases.

Actin regulators in cancer progression and metastases: From structure and function to cytoskeletal dynamics

The cytoskeleton is a central factor contributing to various hallmarks of cancer. In recent years, there has been increasing evidence demonstrating the involvement of actin regulatory proteins in malignancy, and their dysregulation was shown to predict poor clinical prognosis. Although enhanced cytoskeletal activity is often associated with cancer progression, the expression of several inducers of actin polymerization is remarkably reduced in certain malignancies, and it is not completely clear how these changes promote tumorigenesis and metastases. The complexities involved in cytoskeletal induction of cancer progression therefore pose considerable difficulties for therapeutic intervention; it is not always clear which cytoskeletal regulator should be targeted in order to impede cancer progression, and whether this targeting may inadvertently enhance alternative invasive pathways which can aggravate tumor growth. The entire constellation of cytoskeletal machineries in eukaryotic cells are numerous and complex; the system is comprised of and regulated by hundreds of proteins, which could not be covered in a single review. Therefore, we will focus here on the actin cytoskeleton, which encompasses the biological machinery behind most of the key cellular functions altered in cancer, with specific emphasis on actin nucleating factors and nucleation-promoting factors. Finally, we discuss current therapeutic strategies for cancer which aim to target the cytoskeleton.

Endothelial Cell Mechano-Metabolomic Coupling to Disease States in the Lung Microvasculature

Lungs are the most vascular part of humans, accepting the totality of cardiac output in a volume much smaller than the body itself. Due to this cardiac output, the lung microvasculature is subject to mechanical forces including shear stress and cyclic stretch that vary with the cardiac and breathing cycle. Vessels are surrounded by extracellular matrix which dictates the stiffness which endothelial cells also sense and respond to. Shear stress, stiffness, and cyclic stretch are known to influence endothelial cell state. At high shear stress, endothelial cells exhibit cell quiescence marked by low inflammatory markers and high nitric oxide synthesis, whereas at low shear stress, endothelial cells are thought to "activate" into a pro-inflammatory state and have low nitric oxide. Shear stress' profound effect on vascular phenotype is most apparent in the arterial vasculature and in the pathophysiology of vascular inflammation. To conduct the flow of blood from the right heart, the lung microvasculature must be rigid yet compliant. It turns out that excessive substrate rigidity or stiffness is important in the development of pulmonary hypertension and chronic fibrosing lung diseases via excessive cell proliferation or the endothelial-mesenchymal transition. Recently, a new body of literature has evolved that couples mechanical sensing to endothelial phenotypic changes through metabolic signaling in clinically relevant contexts such as pulmonary hypertension, lung injury syndromes, as well as fibrosis, which is the focus of this review. Stretch, like flow, has profound effect on endothelial phenotype; metabolism studies due to stretch are in their infancy.

Shear stress regulation of miR-93 and miR-484 maturation through nucleolin

Pulsatile shear (PS) and oscillatory shear (OS) elicit distinct mechanotransduction signals that maintain endothelial homeostasis or induce endothelial dysfunction, respectively. A subset of microRNAs (miRs) in vascular endothelial cells (ECs) are differentially regulated by PS and OS, but the regulation of the miR processing and its implications in EC biology by shear stress are poorly understood. From a systematic in silico analysis for RNA binding proteins that regulate miR processing, we found that nucleolin (NCL) is a major regulator of miR processing in response to OS and essential for the maturation of miR-93 and miR-484 that target mRNAs encoding Krüppel-like factor 2 (KLF2) and endothelial nitric oxide synthase (eNOS). Additionally, anti-miR-93 and anti-miR-484 restore KLF2 and eNOS expression and NO bioavailability in ECs under OS. Analysis of posttranslational modifications of NCL identified that serine 328 (S328) phosphorylation by AMP-activated protein kinase (AMPK) was a major PS-activated event. AMPK phosphorylation of NCL sequesters it in the nucleus, thereby inhibiting miR-93 and miR-484 processing and their subsequent targeting of KLF2 and eNOS mRNA. Elevated levels of miR-93 and miR-484 were found in sera collected from individuals afflicted with coronary artery disease in two cohorts. These findings provide translational relevance of the AMPK-NCL-miR-93/miR-484 axis in miRNA processing in EC health and coronary artery disease.

SIRT1/AMPK and Akt/eNOS signaling pathways are involved in endothelial protection of total aralosides of Aralia elata (Miq) Seem against high-fat diet-induced atherosclerosis in ApoE-/- mice

Total aralosides of Aralia elata (Miq) Seem (TASAESs) possess multiple pharmacological activity, such as anti-inflammation, antioxidation, and antiapoptosis. However, there is no literature reporting the antiatherosclerotic effect and mechanism of TASAES so far. The aim of this study was to investigate the antiatherosclerotic effects in high-fat diet-induced ApoE-/- mice and potential mechanism of TASAES in ox-LDL-injured endothelial cells. In vivo assay, our data demonstrated that TASAES significantly reduced the atherosclerotic plaque size and caspase-3 expression level in aortic valve. In vitro, we found that TASAES could increase endothelial cell viability, attenuated mitochondrial membrane potential depolarization, and endothelial cells apoptosis. In addition, we found that TASAES could activate SIRT1/AMPK and Akt/eNOS signaling pathways. Importantly, EX527, SIRT1 siRNA, and LY294002, Akt siRNA, remarkably abolished the antiapoptotic effects of TASAES. In conclusion, this study demonstrated that SIRT1/AMPK and Akt/eNOS signaling pathways are involved in endothelial protection of TASAES against atherosclerotic mice, suggesting that TASAES is a candidate drug for atherosclerosis treatment.

Atheroprone flow enhances the endothelial-to-mesenchymal transition

The endothelial-to-mesenchymal transition (EndoMT) is a cellular process featuring decreased expression of endothelial marker genes but increased expression of mesenchymal marker genes. The EndoMT is involved in endothelial dysfunction and the pathogenesis of atherosclerosis. To investigate the dynamic expression of EndoMT genes in vascular endothelial cells under atheroprotective pulsatile shear stress (PS) and atheroprone oscillatory shear stress (OS), we analyzed RNA sequencing data from multitimepoint shear-stress experiments. This unbiased analysis involving next-generation sequencing confirmed that PS and OS had an opposite effect in regulating EndoMT genes. Further experimental validations with H2O2 and gain- and loss-of-function approaches indicated that reactive oxygen species are involved in OS-induced EndoMT, whereas AMP-activated protein kinase and sirtuin-1 could inhibit OS-induced EndoMT. Furthermore, compared with PS, OS increased the DNA methylation of the promoter regions of von Willebrand factor, CD31, and cadherin 5 genes but decreased that of cadherin 2, fibroblast-specific protein 1, and vimentin. The translational implication of the present study builds on the ability of the antidiabetic drug metformin and cholesterol-lowering drug atorvastatin to suppress the EndoMT in cultured endothelial cells and in mouse aortas. NEW & NOTEWORTHY Our RNA sequencing data provided a genome-wide and unbiased view of the shear stress regulation of the endothelial-to-mesenchymal transition (EndoMT) in the endothelium. Furthermore, epigenetic regulation (e.g., DNA methylation) is a key mechanism involved in shear stress-regulated EndoMT. The translational implication of this study is that cardiovascular medications such as statins and metformin have similar beneficial effects as that of atheroprotective flow by mitigating EndoMT.

Endothelial cell regulation through epigenetic mechanisms: Depicting parallels and its clinical application within an intra-islet microenvironment

The intra-islet endothelial cells (ECs), the building blocks of islet microvasculature, govern a number of cellular and pathophysiological processes associated with the pancreatic tissue. These cells are key to the angiogenic process and essential for islet revascularization after transplantation. Understanding fundamental mechanisms by which ECs regulate the angiogenic process is important as these cells maintain and regulate the intra-islet environment facilitated by a complex signaling crosstalk with the surrounding endocrine cells. In recent years, many studies have demonstrated the impact of epigenetic regulation on islet cell development and function. This review will present an overview of the reports involving endothelial epigenetic mechanisms particularly focusing on histone modifications which have been identified to play a critical role in governing EC functions by modifying the chromatin structure. A better understanding of epigenetic mechanisms by which these cells regulate gene expression and function to orchestrate cellular physiology and pathology is likely to offer improved insights on the functioning and regulation of an intra-islet endothelial microvascular environment.

AMP-activated Protein Kinase Phosphorylation of Angiotensin-Converting Enzyme 2 in Endothelium Mitigates Pulmonary Hypertension

RATIONALE

Endothelial dysfunction plays an integral role in pulmonary hypertension (PH). AMPK (AMP-activated protein kinase) and ACE2 (angiotensin-converting enzyme 2) are crucial in endothelial homeostasis. The mechanism by which AMPK regulates ACE2 in the pulmonary endothelium and its protective role in PH remain elusive.

OBJECTIVES

We investigated the role of AMPK phosphorylation of ACE2 Ser680 in ACE2 stability and deciphered the functional consequences of this post-translational modification of ACE2 in endothelial homeostasis and PH.

METHODS

Bioinformatics prediction, kinase assay, and antibody against phospho-ACE2 Ser680 (p-ACE2 S680) were used to investigate AMPK phosphorylation of ACE2 Ser680 in endothelial cells. Using CRISPR-Cas9 genomic editing, we created gain-of-function ACE2 S680D knock-in and loss-of-function ACE2 knockout (ACE2-/-) mouse lines to address the involvement of p-ACE2 S680 and ACE2 in PH. The AMPK-p-ACE2 S680 axis was also validated in lung tissue from humans with idiopathic pulmonary arterial hypertension.

MEASUREMENTS AND MAIN RESULTS

Phosphorylation of ACE2 by AMPK enhanced the stability of ACE2, which increased Ang (angiotensin) 1-7 and endothelial nitric oxide synthase-derived NO bioavailability. ACE2 S680D knock-in mice were resistant to PH as compared with wild-type littermates. In contrast, ACE2-knockout mice exacerbated PH, a similar phenotype found in mice with endothelial cell-specific deletion of AMPKα2. Consistently, the concentrations of phosphorylated AMPK, p-ACE2 S680, and ACE2 were decreased in human lungs with idiopathic pulmonary arterial hypertension.

CONCLUSIONS

Impaired phosphorylation of ACE2 Ser680 by AMPK in pulmonary endothelium leads to a labile ACE2 and hence is associated with the pathogenesis of PH. Thus, AMPK regulation of the vasoprotective ACE2 is a potential target for PH treatment.

Cortactin function in invadopodia

Actin remodeling plays an essential role in diverse cellular processes such as cell motility, vesicle trafficking or cytokinesis. The scaffold protein and actin nucleation promoting factor Cortactin is present in virtually all actin-based structures, participating in the formation of branched actin networks. It has been involved in the control of endocytosis, and vesicle trafficking, axon guidance and organization, as well as adhesion, migration and invasion. To migrate and invade through three-dimensional environments, cells have developed specialized actin-based structures called invadosomes, a generic term to designate invadopodia and podosomes. Cortactin has emerged as a critical regulator of invadosome formation, function and disassembly. Underscoring this role, Cortactin is frequently overexpressed in several types of invasive cancers. Herein we will review the roles played by Cortactin in these specific invasive structures.

Mechanobiology in vascular remodeling

Vascular remodeling is a common pathological process in cardiovascular diseases and includes changes in cell proliferation, apoptosis and differentiation as well as vascular homeostasis. Mechanical stresses, such as shear stress and cyclic stretch, play an important role in vascular remodeling. Vascular cells can sense the mechanical factors through cell membrane proteins, cytoskeletons and nuclear envelope proteins to initiate mechanotransduction, which involves intercellular signaling, gene expression, and protein expression to result in functional regulations. Non-coding RNAs, including microRNAs and long non-coding RNAs, are involved in the regulation of vascular remodeling processes. Mechanotransduction triggers a cascade reaction process through a complicated signaling network in cells. High-throughput technologies in combination with functional studies targeting some key hubs and bridging nodes of the network can enable the prioritization of potential targets for subsequent investigations of clinical translation. Vascular mechanobiology, as a new frontier field of biomechanics, searches for principles of stress-growth in vasculature to elucidate how mechanical factors induce biological effects that lead to vascular remodeling, with the goal of understanding the mechanical basis of the pathological mechanism of cardiovascular diseases at the cellular and molecular levels. Vascular mechanobiology will play a unique role in solving the key scientific problems of human physiology and disease, as well as generating important theoretical and clinical results.

Endothelial Functions

The endothelium plays important roles in modulating vascular tone by synthesizing and releasing a variety of endothelium-derived relaxing factors, including vasodilator prostaglandins, NO, and endothelium-dependent hyperpolarization factors, as well as endothelium-derived contracting factors. Endothelial dysfunction is mainly caused by reduced production or action of these relaxing mediators. Accumulating evidence has demonstrated that endothelial functions are essential to ensure proper maintenance of vascular homeostasis and that endothelial dysfunction is the hallmark of a wide range of cardiovascular diseases associated with pathological conditions toward vasoconstriction, thrombosis, and inflammatory state. In the clinical settings, evaluation of endothelial functions has gained increasing attention in view of its emerging relevance for cardiovascular disease. Recent experimental and clinical studies in the vascular biology field have demonstrated a close relationship between endothelial functions and cardiovascular disease and the highlighted emerging modulators of endothelial functions, new insight into cardiovascular disease associated with endothelial dysfunction, and potential therapeutic and diagnostic targets with major clinical implications. We herein will summarize the current knowledge on endothelial functions from bench to bedside with particular focus on recent publications in Arteriosclerosis, Thrombosis, and Vascular Biology.