MicroRNA-10a is crucial for endothelial response to different flow patterns via interaction of retinoid acid receptors and histone deacetylases

Deciphering the dynamics: Exploring the impact of mechanical forces on histone acetylation

Living cells navigate a complex landscape of mechanical cues that influence their behavior and fate, originating from both internal and external sources. At the molecular level, the translation of these physical stimuli into cellular responses relies on the intricate coordination of mechanosensors and transducers, ultimately impacting chromatin compaction and gene expression. Notably, epigenetic modifications on histone tails govern the accessibility of gene-regulatory sites, thereby regulating gene expression. Among these modifications, histone acetylation emerges as particularly responsive to the mechanical microenvironment, exerting significant control over cellular activities. However, the precise role of histone acetylation in mechanosensing and transduction remains elusive due to the complexity of the acetylation network. To address this gap, our aim is to systematically explore the key regulators of histone acetylation and their multifaceted roles in response to biomechanical stimuli. In this review, we initially introduce the ubiquitous force experienced by cells and then explore the dynamic alterations in histone acetylation and its associated co-factors, including HDACs, HATs, and acetyl-CoA, in response to these biomechanical cues. Furthermore, we delve into the intricate interactions between histone acetylation and mechanosensors/mechanotransducers, offering a comprehensive analysis. Ultimately, this review aims to provide a holistic understanding of the nuanced interplay between histone acetylation and mechanical forces within an academic framework.

Up-regulation of miR-10a-5p expression inhibits the proliferation and differentiation of neural stem cells by targeting Chl1

Neural tube defects (NTDs) are characterized by the failure of neural tube closure during embryogenesis and are considered the most common and severe central nervous system anomalies during early development. Recent microRNA (miRNA) expression profiling studies have revealed that the dysregulation of several miRNAs plays an important role in retinoic acid (RA)-induced NTDs. However, the molecular functions of these miRNAs in NTDs remain largely unidentified. Here, we show that miR-10a-5p is significantly upregulated in RA-induced NTDs and results in reduced cell growth due to cell cycle arrest and dysregulation of cell differentiation. Moreover, the cell adhesion molecule L1-like ( Chl1) is identified as a direct target of miR-10a-5p in neural stem cells (NSCs) in vitro, and its expression is reduced in RA-induced NTDs. siRNA-mediated knockdown of intracellular Chl1 affects cell proliferation and differentiation similar to those of miR-10a-5p overexpression, which further leads to the inhibition of the expressions of downstream ERK1/2 MAPK signaling pathway proteins. These cellular responses are abrogated by either increased expression of the direct target of miR-10a-5p ( Chl1) or an ERK agonist such as honokiol. Overall, our study demonstrates that miR-10a-5p plays a major role in the process of NSC growth and differentiation by directly targeting Chl1, which in turn induces the downregulation of the ERK1/2 cascade, suggesting that miR-10a-5p and Chl1 are critical for NTD formation in the development of embryos.

Recent advances of mechanosensitive genes in vascular endothelial cells for the formation and treatment of atherosclerosis

Atherosclerotic cardiovascular disease and its complications are a high-incidence disease worldwide. Numerous studies have shown that blood flow shear has a huge impact on the function of vascular endothelial cells, and it plays an important role in gene regulation of pro-inflammatory, pro-thrombotic, pro-oxidative stress, and cell permeability. Many important endothelial cell mechanosensitive genes have been discovered, including KLK10, CCN gene family, NRP2, YAP, TAZ, HIF-1α, NF-κB, FOS, JUN, TFEB, KLF2/KLF4, NRF2, and ID1. Some of them have been intensively studied, whereas the relevant regulatory mechanism of other genes remains unclear. Focusing on these mechanosensitive genes will provide new strategies for therapeutic intervention in atherosclerotic vascular disease. Thus, this article reviews the mechanosensitive genes affecting vascular endothelial cells, including classical pathways and some newly screened genes, and summarizes the latest research progress on their roles in the pathogenesis of atherosclerosis to reveal effective therapeutic targets of drugs and provide new insights for anti-atherosclerosis.

Chromatin modifiers in human disease: from functional roles to regulatory mechanisms

The field of transcriptional regulation has revealed the vital role of chromatin modifiers in human diseases from the beginning of functional exploration to the process of participating in many types of disease regulatory mechanisms. Chromatin modifiers are a class of enzymes that can catalyze the chemical conversion of pyrimidine residues or amino acid residues, including histone modifiers, DNA methyltransferases, and chromatin remodeling complexes. Chromatin modifiers assist in the formation of transcriptional regulatory circuits between transcription factors, enhancers, and promoters by regulating chromatin accessibility and the ability of transcription factors to acquire DNA. This is achieved by recruiting associated proteins and RNA polymerases. They modify the physical contact between cis-regulatory factor elements, transcription factors, and chromatin DNA to influence transcriptional regulatory processes. Then, abnormal chromatin perturbations can impair the homeostasis of organs, tissues, and cells, leading to diseases. The review offers a comprehensive elucidation on the function and regulatory mechanism of chromatin modifiers, thereby highlighting their indispensability in the development of diseases. Furthermore, this underscores the potential of chromatin modifiers as biomarkers, which may enable early disease diagnosis. With the aid of this paper, a deeper understanding of the role of chromatin modifiers in the pathogenesis of diseases can be gained, which could help in devising effective diagnostic and therapeutic interventions.

Non-canonical retinoid signaling in neural development, regeneration and synaptic function

Canonical retinoid signaling via nuclear receptors and gene regulation is critical for the initiation of developmental processes such as cellular differentiation, patterning and neurite outgrowth, but also mediates nerve regeneration and synaptic functions in adult nervous systems. In addition to canonical transcriptional regulation, retinoids also exert rapid effects, and there are now multiple lines of evidence supporting non-canonical retinoid actions outside of the nucleus, including in dendrites and axons. Together, canonical and non-canonical retinoid signaling provide the precise temporal and spatial control necessary to achieve the fine cellular coordination required for proper nervous system function. Here, we examine and discuss the evidence supporting non-canonical actions of retinoids in neural development and regeneration as well as synaptic function, including a review of the proposed molecular mechanisms involved.

The role of metabolism in cardiac development

Metabolism is the fundamental process that sustains life. The heart, in particular, is an organ of high energy demand, and its energy substrates have been studied for more than a century. In recent years, there has been a growing interest in understanding the role of metabolism in the early differentiation of pluripotent stem cells and in cancer research. Studies have revealed that metabolic intermediates from glycolysis and the tricarboxylic acid cycle act as co-factors for intracellular signal transduction, playing crucial roles in regulating cell behaviors. Mitochondria, as the central hub of metabolism, are also under intensive investigation regarding the regulation of their dynamics. The metabolic environment of the fetus is intricately linked to the maternal metabolic status, and the impact of the mother's nutrition and metabolic health on fetal development is significant. For instance, it is well known that maternal diabetes increases the risk of cardiac and nervous system malformations in the fetus. Another notable example is the decrease in the risk of neural tube defects when pregnant women are supplemented with folic acid. These examples highlight the profound influence of the maternal metabolic environment on the fetal organ development program. Therefore, gaining insights into the metabolic environment within developing fetal organs is critical for deepening our understanding of normal organ development. This review aims to summarize recent findings that build upon the historical recognition of the environmental and metabolic factors involved in the developing embryo.

Exploring the nexus of nuclear receptors in hematological malignancies

Hematological malignancies (HM) represent a subset of neoplasms affecting the blood, bone marrow, and lymphatic systems, categorized primarily into leukemia, lymphoma, and multiple myeloma. Their prognosis varies considerably, with a frequent risk of relapse despite ongoing treatments. While contemporary therapeutic strategies have extended overall patient survival, they do not offer cures for advanced stages and often lead to challenges such as acquisition of drug resistance, recurrence, and severe side effects. The need for innovative therapeutic targets is vital to elevate both survival rates and patients' quality of life. Recent research has pivoted towards nuclear receptors (NRs) due to their role in modulating tumor cell characteristics including uncontrolled proliferation, differentiation, apoptosis evasion, invasion and migration. Existing evidence emphasizes NRs' critical role in HM. The regulation of NR expression through agonists, antagonists, or selective modulators, contingent upon their levels, offers promising clinical implications in HM management. Moreover, several anticancer agents targeting NRs have been approved by the Food and Drug Administration (FDA). This review highlights the integral function of NRs in HM's pathophysiology and the potential benefits of therapeutically targeting these receptors, suggesting a prospective avenue for more efficient therapeutic interventions against HM.

[Investigation of the mechanism of action and identification of candidate traditional Chinese medicines for the treatment of ischemic stroke in the Danshen-Jiangxiang pair based on drug-target-disease association network]

The therapeutic efficacy of Danshen and Jiangxiang in the treatment of ischemic stroke (IS) is relatively significant. Studying the mechanism of action of Danshen and Jiangxiang in the treatment of IS can effectively identify candidate traditional Chinese medicines (TCM) with efficacy. However, it is challenging to analyze the effector substances and explain the mechanism of action of Danshen-Jiangxiang from a systematic perspective using traditional pharmacological approaches. In this study, a systematic study was conducted based on the drug-target-symptom-disease association network using complex network theory. On the basis of the association information about Danshen, Jiangxiang and IS, the protein-protein interaction (PPI) network and the "drug pair-pharmacodynamic ingredient-target-IS" network were constructed. The different topological features of the networks were analyzed to identify the core pharmacodynamic ingredients including formononetin in Jiangxiang, cryptotanshinone and tanshinone IIA in Danshen as well as core target proteins such as prostaglandin G/H synthase 2, retinoic acid receptor RXR-alpha, sodium channel protein type 5 subunit alpha, prostaglandin G/H synthase 1 and beta-2 adrenergic receptor. Further, a method for screening IS candidates based on TCM symptoms was proposed to identify key TCM symptoms and syndromes using the "drug pair-TCM symptom-syndrome-IS" network. The results showed that three TCMs, namely Puhuang, Sanleng and Zelan, might be potential therapeutic candidates for IS, which provided a theoretical reference for the development of drugs for the treatment of IS.

Endothelial Gata6 deletion reduces monocyte recruitment and proinflammatory macrophage formation and attenuates atherosclerosis through Cmpk2-Nlrp3 pathways

Endothelial dysfunction results in chronic vascular inflammation, which is critical for the development of atherosclerotic diseases. Transcription factor Gata6 has been reported to regulate vascular endothelial cell activation and inflammation in vitro. Here, we aimed to explore the roles and mechanisms of endothelial Gata6 in atherogenesis. Endothelial cell (EC) specific Gata6 deletion was generated in the ApoeKO hyperlipidemic atherosclerosis mouse model. Atherosclerotic lesion formation, endothelial inflammatory signaling, and endothelial-macrophage interaction were examined in vivo and in vitro by using cellular and molecular biological approaches. EC-GATA6 deletion mice exhibited a significant decrease in monocyte infiltration and atherosclerotic lesion compared to littermate control mice. Cytosine monophosphate kinase 2 (Cmpk2) was identified as a direct target gene of GATA6 and EC-GATA6 deletion decreased monocyte adherence, migration and pro-inflammatory macrophage foam cell formation through regulation of the CMPK2-Nlrp3 pathway. Endothelial target delivery of Cmpk2-shRNA by intercellular adhesion molecule 2 (Icam-2) promoter-driven AAV9 carrying the shRNA reversed the Gata6 upregulation mediated elevated Cmpk2 expression and further Nlrp3 activation and thus attenuated atherosclerosis. In addition, C-C motif chemokine ligand 5 (Ccl5) was also identified as a direct target gene of Gata6 to regulate monocyte adherence and migration influencing atherogenesis. This study provides direct in vivo evidence of EC-GATA6 involvement in the regulation of Cmpk2-Nlrp3, as well as Ccl5, on monocyte adherence and migration in atherosclerosis development and advances our understanding of the in vivo mechanisms of atherosclerotic lesion development, and meanwhile provides opportunities for future therapeutic interventions.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Mechanotransduction of mesenchymal stem cells and hemodynamic implications

Mesenchymal stem cells (MSCs) possess the capacity for self-renewal and multipotency. The traditional approach to manipulating MSC's fate choice predominantly relies on biochemical stimulation. Accumulating evidence also suggests the role of physical input in MSCs differentiation. Therefore, investigating mechanotransduction at the molecular level and related to tissue-specific cell functions sheds light on the responses secondary to mechanical forces. In this review, a new frontier aiming to optimize the cultural parameters was illustrated, i.e. spatial boundary condition, which recapitulates in vivo physiology and facilitates the investigations of cellular behavior. The concept of mechanical memory was additionally addressed to appreciate how MSCs store imprints from previous culture niches. Besides, different types of forces as physical stimuli were of interest based on the association with the respective signaling pathways and the differentiation outcome. The downstream mechanoreceptors and their corresponding effects were further pinpointed. The cardiovascular system or immune system may share similar mechanisms of mechanosensing and mechanotransduction; for example, resident stem cells in a vascular wall and recruited MSCs in the bloodstream experience mechanical forces such as stretch and fluid shear stress. In addition, baroreceptors or mechanosensors of endothelial cells detect changes in blood flow, pass over signals induced by mechanical stimuli and eventually maintain arterial pressure at the physiological level. These mechanosensitive receptors transduce pressure variation and regulate endothelial barrier functions. The exact signal transduction is considered context dependent but still elusive. In this review, we summarized the current evidence of how mechanical stimuli impact MSCs commitment and the underlying mechanisms. Future perspectives are anticipated to focus on the application of cardiovascular bioengineering and regenerative medicine.

Blood Reflux-Induced Epigenetic Factors HDACs and DNMTs Are Associated with the Development of Human Chronic Venous Disease

Blood reflux and metabolic regulation play important roles in chronic venous disease (CVD) development. Histone deacetylases (HDACs) and DNA methyltransferases (DNMTs) serve as repressors that inhibit metabolic signaling, which is induced by proatherogenic flow to promote aortic endothelial cell (EC) dysfunction and atherosclerosis. The aim of this study was to elucidate the relationship between blood reflux and epigenetic factors HDACs and DNMTs in CVD. Human varicose veins with different levels of blood reflux versus normal veins with normal venous flow were examined. The results show that HDAC-1, -2, -3, -5, and -7 are overexpressed in the endothelium of varicose veins with blood reflux. Blood reflux-induced HDACs are enhanced in the varicose veins with a longer duration time of blood reflux. In contrast, these HDACs are rarely expressed in the endothelium of the normal vein with normal venous flow. Similar results are obtained for DNMT1 and DNMT3a. Our findings suggest that the epigenetic factors, HDACs and DNMTs, are induced in venous ECs in response to blood reflux but are inhibited in response to normal venous flow. Blood reflux-induced HDACs and DNMTs could inhibit metabolic regulation and promote venous EC dysfunction, which is highly correlated with CVD pathogenesis.

Circadian clock-mediated nuclear receptors in cancer

Circadian system coordinates the daily periodicity of physiological and biochemical functions to adapt to environmental changes. Circadian disruption has been identified to increase the risk of cancer and promote cancer progression, but the underlying mechanism remains unclear. And further mechanistic understanding of the crosstalk between clock components and cancer is urgent to achieve clinical anticancer benefits from chronochemotherapy. Recent studies discover that several nuclear receptors regulating circadian clock, also play crucial roles in mediating multiple cancer processes. In this review, we aim to summarize the latest developments of clock-related nuclear receptors in cancer biology and dissect mechanistic insights into how nuclear receptors coordinate with circadian clock to regulate tumorigenesis and cancer treatment. A better understanding of circadian clock-related nuclear receptors in cancer could help prevent tumorigenesis and improve anticancer efficacy.

Chromatin condensation regulates endothelial cell adaptation to shear stress

Vascular endothelial cells (ECs) have been shown to be mechanoresponsive to the forces of blood flow, including fluid shear stress (FSS), the frictional force of blood on the vessel wall. Recent reports have shown that FSS induces epigenetic changes in chromatin. Epigenetic changes, such as methylation and acetylation of histones, not only affect gene expression but also affect chromatin condensation, which can alter nuclear stiffness. Thus, we hypothesized that changes in chromatin condensation may be an important component for how ECs adapt to FSS. Using both in vitro and in vivo models of EC adaptation to FSS, we observed an increase in histone acetylation and a decrease in histone methylation in ECs adapted to flow as compared with static. Using small molecule drugs, as well as vascular endothelial growth factor, to change chromatin condensation, we show that decreasing chromatin condensation enables cells to more quickly align to FSS, whereas increasing chromatin condensation inhibited alignment. Additionally, we show data that changes in chromatin condensation can also prevent or increase DNA damage, as measured by phosphorylation of γH2AX. Taken together, these results indicate that chromatin condensation, and potentially by extension nuclear stiffness, is an important aspect of EC adaptation to FSS.

MicroRNAs in Mechanical Homeostasis

Mechanical variables such as stiffness, stress, strain, and fluid shear stress are central to tissue functions, thus, must be maintained within the proper range. Mechanics are especially important in the cardiovascular system and lung, the functions of which are essentially mechanical. Mechanical homeostasis is characterized by negative feedback in which deviations from the optimal value or set point activates mechanisms to return the system to the correct range. In chronic diseases, homeostatic mechanisms are generally overcome or replaced with positive feedback loops that promote disease progression. Recent work has shown that microRNAs (miRNAs) are essential to mechanical homeostasis in a number of biological systems and that perturbations to miRNA biogenesis play key roles in cardiovascular and pulmonary diseases. In this review, we integrate current knowledge of miRNAs in mechanical homeostasis and how these mechanisms are altered in disease.

An integrated approach to understand fluid shear stress-driven and reactive oxygen species-mediated metastasis of colon adenocarcinoma through mRNA-miRNA-lncRNA-circRNA networks

Development of colon adenocarcinoma (COAD) metastasis involves several mediators including fluid shear stress (FSS), intracellular ROS levels, and non-coding RNAs. In our present study, we identified and investigated the role of regulatory non-coding RNA molecules specifically involved in COAD metastasis and their association with FSS and ROS. Interactions between the mRNAs associated with FSS and ROS, the corresponding microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) in COAD metastasis were used to generate the mRNA-miRNA-lncRNA-circRNA network. Experimental validation of the identified RNA hubs using quantitative real-time PCR demonstrated a direct effect of the FSS on their expression levels in cancer cells. FSS resulted in the downregulation of HMGA1 and RAN, as well as the upregulation of HSP90AA1, PMAIP1 and BIRC5. Application of shear stress also led to downregulation of hsa-miR-26b-5p and hsa-miR-34a-5p levels in HCT116 cells. Further, functional enrichment and survival analysis of the significant miRNAs, as well as the OncoPrint and the survival analyses of the selected mRNAs were performed. Subsequently, their functional role was also corroborated with existing literature. Ten significant miRNA hubs were identified, out of which hsa-miR-17-5p and hsa-miR-20a-5p were found to interact with lncRNA (CCAT2) while hsa-miR-335 was found to interact with four circRNAs. Fifteen significant miRNAs were identified in 10 different modules suggesting their importance in FSS and ROS-mediated COAD metastasis. Finally, 10 miRNAs and 3 mRNAs associated with FSS and/or ROS were identified as significant overall survival markers; 33 mRNAs were also identified as metastasis-free survival markers whereas 15 mRNAs showed > 10% gene alterations in TCGA-COAD data and may serve as promising therapeutic biomarkers in the COAD metastasis.

Endothelial shear stress signal transduction and atherogenesis: From mechanisms to therapeutics

Atherosclerotic vascular disease and its complications are among the top causes of mortality worldwide. In the vascular lumen, atherosclerotic plaques are not randomly distributed. Instead, they are preferentially localized at the curvature and bifurcations along the arterial tree, where shear stress is low or disturbed. Numerous studies demonstrate that endothelial cell phenotypic change (e.g., inflammation, oxidative stress, endoplasmic reticulum stress, apoptosis, autophagy, endothelial-mesenchymal transition, endothelial permeability, epigenetic regulation, and endothelial metabolic adaptation) induced by oscillatory shear force play a fundamental role in the initiation and progression of atherosclerosis. Mechano-sensors, adaptor proteins, kinases, and transcriptional factors work closely at different layers to transduce the shear stress force from the plasma membrane to the nucleus in endothelial cells, thereby controlling the expression of genes that determine cell fate and phenotype. An in-depth understanding of these mechano-sensitive signaling cascades shall provide new translational strategies for therapeutic intervention of atherosclerotic vascular disease. This review updates the recent advances in endothelial mechano-transduction and its role in the pathogenesis of atherosclerosis, and highlights the perspective of new anti-atherosclerosis therapies through targeting these mechano-regulated signaling molecules.

Histone Deacetylases and Their Potential as Targets to Enhance Tumour Radiosensitisation

In mammalian cells, genomic DNA is packaged with histone proteins and condensed into chromatin. To gain access to the DNA, chromatin remodelling is required that is enhanced through histone post-translational modifications, which subsequently stimulate processes including DNA repair and transcription. Histone acetylation is one of the most well understood modifications and is controlled by histone acetyltransferases (HATs) and histone deacetylases (HDACs). These enzymes play critical roles in normal cellular functioning, and the dysregulation of HDAC expression in particular has been linked with the development of a number of different cancer types. Conversely, tumour cell killing following radiotherapy is triggered through DNA damage and HDACs can help co-ordinate the cellular DNA damage response which promotes radioresistance. Consequently, HDAC inhibitors have been investigated as potential radiosensitizers in vitro and in vivo to improve the efficacy or radiotherapy in specific tumour types. In this review, we provide an up-to-date summary of HDACs and their cellular functions, including in DNA damage repair. We also review evidence demonstrating that HDAC inhibitors can effectively enhance tumour radiosensitisation, and which therefore show potential for translation into the clinic for cancer patient benefit.

Flow-Responsive Noncoding RNAs in the Vascular System: Basic Mechanisms for the Clinician

The vascular system is largely exposed to the effect of changing flow conditions. Vascular cells can sense flow and its changes. Flow sensing is of pivotal importance for vascular remodeling. In fact, it influences the development and progression of atherosclerosis, controls its location and has a major influx on the development of local complications. Despite its importance, the research community has traditionally paid scarce attention to studying the association between different flow conditions and vascular biology. More recently, a growing body of evidence has been accumulating, revealing that ncRNAs play a key role in the modulation of several biological processes linking flow-sensing to vascular pathophysiology. This review summarizes the most relevant evidence on ncRNAs that are directly or indirectly responsive to flow conditions to the benefit of the clinician, with a focus on the underpinning mechanisms and their potential application as disease biomarkers.

METTL3-dependent N6-methyladenosine RNA modification mediates the atherogenic inflammatory cascades in vascular endothelium

Atherosclerosis is characterized by the plaque formation that restricts intraarterial blood flow. The disturbed blood flow with the associated oscillatory stress (OS) at the arterial curvatures and branch points can trigger endothelial activation and is one of the risk factors of atherosclerosis. Many studies reported the mechanotransduction related to OS and atherogenesis; however, the transcriptional and posttranscriptional regulatory mechanisms of atherosclerosis remain unclear. Herein, we investigated the role of N⁶-methyladenosine (m⁶A) RNA methylation in mechanotransduction in endothelial cells (ECs) because of its important role in epitranscriptome regulation. We have identified m⁶A methyltransferase METTL3 as a responsive hub to hemodynamic forces and atherogenic stimuli in ECs. OS led to an up-regulation of METTL3 expression, accompanied by m⁶A RNA hypermethylation, increased NF-κB p65 Ser⁵³⁶ phosphorylation, and enhanced monocyte adhesion. Knockdown of METTL3 abrogated this OS-induced m⁶A RNA hypermethylation and other manifestations, while METTL3 overexpression led to changes resembling the OS effects. RNA-sequencing and m⁶A-enhanced cross-linking and immunoprecipitation (eCLIP) experiments revealed NLRP1 and KLF4 as two hemodynamics-related downstream targets of METTL3-mediated hypermethylation. The METTL3-mediated RNA hypermethylation up-regulated NLRP1 transcript and down-regulated KLF4 transcript through YTHDF1 and YTHDF2 m⁶A reader proteins, respectively. In the in vivo atherosclerosis model, partial ligation of the carotid artery led to plaque formation and up-regulation of METTL3 and NLRP1, with down-regulation of KLF4; knockdown of METTL3 via repetitive shRNA administration prevented the atherogenic process, NLRP3 up-regulation, and KLF4 down-regulation. Collectively, we have demonstrated that METTL3 serves a central role in the atherogenesis induced by OS and disturbed blood flow.

Low Levels of MicroRNA-10a in Cardiovascular Endothelium and Blood Serum Are Related to Human Atherosclerotic Disease

Background

MicroRNA-10a (miR-10a) inhibits transcriptional factor GATA6 to repress inflammatory GATA6/VCAM-1 signaling, which is regulated by blood flow to affect endothelial function/dysfunction. This study aimed to identify the expression patterns of miR-10a/GATA6/VCAM-1 in vivo and study their implications in the pathophysiology of human coronary artery disease (CAD), i.e., atherosclerosis.

Methods

Human atherosclerotic coronary arteries and nondiseased arteries were used to detect the expressions of miR-10a/GATA6/VCAM-1 in pathogenic vs. normal conditions. In addition, sera from CAD patients and healthy subjects were collected to detect the level of circulating miR-10a.

Results

The comparison of human atherosclerotic coronary arteries with nondiseased arteries demonstrated that lower levels of endothelial miR-10a are related to human atherogenesis. Moreover, GATA6/VCAM-1 (a downstream target of miR-10a) was highly expressed in the endothelium, accompanied by the reduced levels of miR-10a during the development of human atherosclerosis. In addition, CAD patients had a significantly lower concentration of miR-10a in their serum compared to healthy subjects.

Conclusions

Our findings suggest that low miR-10a and high GATA6/VCAM-1 in the cardiovascular endothelium correlates to the development of human atherosclerotic lesions, suggesting that miR-10a signaling has the potential to be developed as a biomarker for human atherosclerosis.

Cell-specific epigenetic changes in atherosclerosis

Atherosclerosis is a disease of large and medium arteries that can lead to life-threatening cerebrovascular and cardiovascular consequences such as heart failure and stroke and is a major contributor to cardiovascular-related mortality worldwide. Atherosclerosis development is a complex process that involves specific structural, functional and transcriptional changes in different vascular cell populations at different stages of the disease. The application of single-cell RNA sequencing (scRNA-seq) analysis has discovered not only disease-related cell-specific transcriptomic profiles but also novel subpopulations of cells once thought as homogenous cell populations. Vascular cells undergo specific transcriptional changes during the entire course of the disease. Epigenetics is the instruction-set-architecture in living cells that defines and maintains the cellular identity by regulating the cellular transcriptome. Although different cells contain the same genetic material, they have different epigenomic signatures. The epigenome is plastic, dynamic and highly responsive to environmental stimuli. Modifications to the epigenome are driven by an array of epigenetic enzymes generally referred to as writers, erasers and readers that define cellular fate and destiny. The reversibility of these modifications raises hope for finding novel therapeutic targets for modifiable pathological conditions including atherosclerosis where the involvement of epigenetics is increasingly appreciated. This article provides a critical review of the up-to-date research in the field of epigenetics mainly focusing on in vivo settings in the context of the cellular role of individual vascular cell types in the development of atherosclerosis.

Inhibition of retinoic acid receptor α phosphorylation represses the progression of triple-negative breast cancer via transactivating miR-3074-5p to target DHRS3

BACKGROUND

Retinoids are promising agents in the treatment of different types of neoplasia including estrogen receptor-positive breast cancers, whereas refractoriness/low sensitivity is observed in triple-negative breast cancer (TNBC) subtype. However, the reason for these diverse retinoid-sensitivity remains elusive.

METHODS

Determinants of retinoid sensitivity were investigated using immunohistochemistry of primary patient samples, and identified retinoic acid receptor α (RARα) as a putative factor. The anti-tumor activity of hypo-phosphorylated RARα was investigated in TNBC cell models and a xenograft mouse model. Next, miRNA sequencing analysis was performed to identify the target miRNA of RARα, and luciferase reporter was used to confirm the direct target gene of miR-3074-5p.

RESULTS

We discovered that serine-77 residue of RARα was constantly phosphorylated, which correlated with TNBC's resistance to retinoids. Overexpression of a phosphorylation-defective mutant RARαS77A mimicked activated RARα and repressed TNBC cell progression both in vitro and in vivo, via activating cell cycle arrest, apoptosis, and cytotoxic autophagy, independent of RARα agonists. We further revealed that the anti-tumor action of RARαS77A was, at least in part, mediated by the up-regulation of miR-3074-5p, which directly targeted DHRS3, a reductase negatively associated with TNBC patient survival. Our results suggest that the inhibition of RARαS77 phosphorylation by either expressing RARαS77A or inhibiting RARα's phosphokinase CDK7, can bypass RA stimuli to transactivate tumor-suppressive miR-3074-5p and reduce oncogenic DHRS3, thus overcoming the RA-resistance of TNBC.

CONCLUSION

The novel regulatory network, involving RARαS77 phosphorylation, miR-3074-5p, and DHRS3, emerges as a new target for TNBC treatment.

Mechanoresponsive Smad5 Enhances MiR-487a Processing to Promote Vascular Endothelial Proliferation in Response to Disturbed Flow

MicroRNAs (miRs) and bone morphogenetic protein receptor-specific Smads are mechano-responsive molecules that play vital roles in modulating endothelial cell (EC) functions in response to blood flow. However, the roles of interplay between these molecules in modulating EC functions under flows remain unclear. We elucidated the regulatory roles of the interplay between miR-487a and Smad5 in EC proliferation in response to different flow patterns. Microarray and quantitative RT-PCR showed that disturbed flow with low and oscillatory shear stress (OS, 0.5 ± 4 dynes/cm²) upregulates EC miR-487a in comparison to static controls and pulsatile shear stress (12 ± 4 dynes/cm²). MiR-487a expression was higher in ECs in the inner curvature (OS region) than the outer curvature of the rat aortic arch and thoracic aorta and also elevated in diseased human coronary arteries. MiR-487a expression was promoted by nuclear phospho-Smad5, which bound to primary-miR-487a to facilitate miR-487a processing. Algorithm prediction and luciferase reporter and argonaute 2-immunoprecipitation assays demonstrated that miR-487a binds to 3'UTR of CREB binding protein (CBP) and p53. Knockdown and overexpression of miR-487a decreased and increased, respectively, phospho-Rb and cyclin A expressions through CBP and p53. A BrdU incorporation assay showed that miR-487a enhanced EC proliferation under OS in vitro and in disturbed flow regions of experimentally stenosed rat abdominal aorta in vivo. These results demonstrate that disturbed flow with OS induces EC expression of miR-487a through its enhanced processing by activated-Smad5. MiR-487 inhibits its direct targets CBP and p53 to induce EC cycle progression and proliferation. Our findings suggest that EC miR-487 may serve as an important molecular target for intervention against disturbed flow-associated vascular disorders resulting from atherosclerosis.

Micro/nano materials regulate cell morphology and intercellular communication by extracellular vesicles

Extracellular vesicles (EVs) have emerged as important nano-cargo carriers for cell-cell communication, yet how biophysical factors regulate EV-mediated signaling is not well understood. Here we show that microgrooves can modulate the morphology of endothelial cells (ECs), and regulate the phenotype of smooth muscle cells (SMCs) through EVs in co-culture. Elongated ECs, in comparison with polygonal ECs, increased the expression of contractile markers in SMCs. Depletion of EVs in the culture medium abolished this effect. Further analysis demonstrated that elongated ECs significantly upregulated miR-143/miR-145, leading to the increase of these microRNAs in EC-secreted EVs that were transferred to SMCs under a co-culture condition. Inhibition of EV secretion from ECs abolished the EC-SMC communication and the increased expression of SMC contractile markers. Moreover, electrospun nano-fibrous scaffolds with aligned fibers had the same effects as microgrooves to induce EC secretion of EVs to regulate SMC phenotypic marker expression. These results demonstrate that micro and nano materials can be used to engineer cell morphology and regulate EV secretion for cell-cell communication, which will have significant implications in the engineering of blood vessels and other tissues. STATEMENT OF SIGNIFICANCE: By manipulating EC morphology with micro/nano materials, we show that EV-mediated signaling can regulate SMC phenotypic marker expression. This is a very thorough and unique study to demonstrate the function of extracellular vesicles (EVs) as important nano-carriers in cell-cell communication. The originality of this study is to demonstrate that EC morphology modulates the phenotype of smooth muscle cells via extracellular vesicles enclosing miR143/miR145. These findings underscore the important role of biophysical changes in cell-cell communications, and provide a rational basis for engineering micro/nano materials to control cell-cell communications for cell and tissue engineering.

HDAC1 and 2 regulate endothelial VCAM-1 expression and atherogenesis by suppressing methylation of the GATA6 promoter

Increased expression of vascular cell adhesion molecule (VCAM)-1 on the activated arterial endothelial cell (EC) surface critically contributes to atherosclerosis which may in part be regulated by epigenetic mechanisms. This study investigated whether and how the clinically available histone deacetylases 1 and 2 (HDAC1/2) inhibitor drug Romidepsin epigenetically modulates VCAM-1 expression to suppress atherosclerosis.

Methods: VCAM-1 expression was analyzed in primary human aortic EC (HAEC) treated with Romidepsin or transfected with HDAC1/2-targeting siRNA. Methylation of GATA6 promoter region was examined with methylation-specific PCR assay. Enrichment of STAT3 to GATA6 promoter was detected with chromatin immunoprecipitation. Lys685Arg mutation was constructed to block STAT3 acetylation. The potential therapeutic effect of Romidepsin on atherosclerosis was evaluated in Apoe^-/- mice fed with a high-fat diet.

Results: Romidepsin significantly attenuated TNFα-induced VCAM-1 expression on HAEC surface and monocyte adhesion through simultaneous inhibition of HDAC1/2. This downregulation of VCAM-1 was attributable to reduced expression of transcription factor GATA6. Romidepsin enhanced STAT3 acetylation and its binding to DNA methyltransferase 1 (DNMT1), leading to hypermethylation of the GATA6 promoter CpG-rich region at +140/+255. Blocking STAT3 acetylation at Lys685 disrupted DNMT1-STAT3 interaction, decreased GATA6 promoter methylation, and reversed the suppressive effects of HDAC1/2 inhibition on GATA6 and VCAM-1 expression. Finally, intraperitoneal administration of Romidepsin reduced diet-induced atherosclerotic lesion development in Apoe^-/- mice, accompanied by a reduction in GATA6/VCAM-1 expression in the aorta.

Conclusions: HDAC1/2 contributes to VCAM-1 expression and atherosclerosis by suppressing STAT3 acetylation-dependent GATA6 promoter methylation. These findings may provide a rationale for HDAC1/2-targeting therapy in atherosclerotic heart disease.

Effects of Shear Stress on Production of FVIII and vWF in a Cell-Based Therapeutic for Hemophilia A

Microfluidic technology enables recapitulation of organ-level physiology to answer pertinent questions regarding biological systems that otherwise would remain unanswered. We have previously reported on the development of a novel product consisting of human placental cells (PLC) engineered to overexpress a therapeutic factor VIII (FVIII) transgene, mcoET3 (PLC-mcoET3), to treat Hemophilia A (HA). Here, microfluidic devices were manufactured to model the physiological shear stress in liver sinusoids, where infused PLC-mcoET3 are thought to lodge after administration, to help us predict the therapeutic outcome of this novel biological strategy. In addition to the therapeutic transgene, PLC-mcoET3 also constitutively produce endogenous FVIII and von Willebrand factor (vWF), which plays a critical role in FVIII function, immunogenicity, stability, and clearance. While vWF is known to respond to flow by changing conformation, whether and how shear stress affects the production and secretion of vWF and FVIII has not been explored. We demonstrated that exposure of PLC-mcoET3 to physiological levels of shear stress present within the liver sinusoids significantly reduced mRNA levels and secreted FVIII and vWF when compared to static conditions. In contrast, mRNA for the vector-encoded mcoET3 was unaltered by flow. To determine the mechanism responsible for the observed decrease in FVIII and vWF mRNA, PCR arrays were performed to evaluate expression of genes involved in shear mechanosensing pathways. We found that flow conditions led to a significant increase in KLF2, which induces miRNAs that negatively regulate expression of FVIII and vWF, providing a mechanistic explanation for the reduced expression of these proteins in PLC under conditions of flow. In conclusion, microfluidic technology allowed us to unmask novel pathways by which endogenous FVIII and vWF are affected by shear stress, while demonstrating that expression of the therapeutic mcoET3 gene will be maintained in the gene-modified PLCs upon transplantation, irrespective of whether they engraft within sites that expose them to conditions of shear stress.

Endothelial Reprogramming by Disturbed Flow Revealed by Single-Cell RNA and Chromatin Accessibility Study

Disturbed flow (d-flow) induces atherosclerosis by regulating gene expression in endothelial cells (ECs). For further mechanistic understanding, we carried out a single-cell RNA sequencing (scRNA-seq) and scATAC-seq study using endothelial-enriched single cells from the left- and right carotid artery exposed to d-flow (LCA) and stable-flow (s-flow in RCA) using the mouse partial carotid ligation (PCL) model. We find eight EC clusters along with immune cells, fibroblasts, and smooth muscle cells. Analyses of marker genes, pathways, and pseudotime reveal that ECs are highly heterogeneous and plastic. D-flow induces a dramatic transition of ECs from atheroprotective phenotypes to pro-inflammatory cells, mesenchymal (EndMT) cells, hematopoietic stem cells, endothelial stem/progenitor cells, and an unexpected immune cell-like (EndICLT) phenotypes. While confirming KLF4/KLF2 as an s-flow-sensitive transcription factor binding site, we also find those sensitive to d-flow (RELA, AP1, STAT1, and TEAD1). D-flow reprograms ECs from atheroprotective to proatherogenic phenotypes, including EndMT and potentially EndICLT.

Non-Coding RNAs and Hereditary Hemorrhagic Telangiectasia

Non-coding RNAs (ncRNAs) are functional ribonucleic acid (RNA) species that include microRNAs (miRs), a class of short non-coding RNAs (∼21–25 nucleotides), and long non-coding RNAs (lncRNAs) consisting of more than 200 nucleotides. They regulate gene expression post-transcriptionally and are involved in a wide range of pathophysiological processes. Hereditary hemorrhagic telangiectasia (HHT) is a rare disorder inherited in an autosomal dominant fashion characterized by vascular dysplasia. Patients can develop life-threatening vascular malformations and experience severe hemorrhaging. Effective pharmacological therapies are limited. The study of ncRNAs in HHT is an emerging field with great promise. This review will explore the current literature on the involvement of ncRNAs in HHT as diagnostic and pathogenic factors.

Differential Expression of Circulating Plasma miRNA-370 and miRNA-10a from Patients with Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant, vascular disorder that presents with telangiectases and arteriovenous malformations. HHT is a genetically heterogeneous disorder, involving mutations in endoglin (ENG; HHT1) and activin receptor-like kinase 1 (ACVRL1/ALK1; HHT2) genes that account for over 85% of all HHT patients. The current diagnosis of HHT patients remains at the clinical level, but many suspected patients do not have a clear HHT diagnosis or do not show pathogenic mutations in HHT genes. This situation has prompted the search for biomarkers to help in the early diagnosis of the disease. We have analyzed the plasma levels in HHT patients of selected micro-RNAs (miRNAs), small single-stranded RNAs that regulate gene expression at the transcriptional level by interacting with specific RNA targets. A total of 16 HHT1 and 17 HHT2 plasma samples from clinically confirmed patients and 16 controls were analyzed in this study. Total RNA was purified from plasma, and three selected miRNAs (miRNA-10a, miRNA-214, and miRNA-370), related to the pathobiology of cardiovascular diseases and potentially targeting ENG or ALK1, were measured by quantitative polymerase chain reaction. Compared with controls, levels of miRNA-370, whose putative target is ENG, were significantly downregulated in HHT1, but not in HHT2, whereas the levels of miRNA-10a, whose putative target is ALK1, were significantly upregulated in HHT2, but not in HHT1. In addition, the levels of miRNA-214, potentially targeting ENG and ALK1, did not change in either HHT1 or HHT2 patients versus control samples. While further studies are warranted, these results suggest that dysregulated plasma levels of miRNA-370 or miRNA-10a could help to identify undiagnosed HHT1 or HHT2 patients, respectively.

Non-coding RNAs as Epigenetic Gene Regulators in Cardiovascular Diseases

Epigenetic gene regulations can be considered as de-novo initiation of abnormal molecular signaling events whose regulation is otherwise required during normal or specific developmental stages of the organisms. Primarily, three different mechanisms have been identified to participate in epigenetic gene regulations which include, DNA methylation, non-coding RNA species (microRNAs [miRNA], and long non-coding RNAs [LNC-RNA]) and histone modifications. These de-novo epigenetic mechanisms have been associated with altered normal cellular functions which eventually facilitate normal cells to transition into an abnormal phenotype. Among the three modes of regulation, RNA species which are usually considered to be less stable, can be speculated to initiate instant alterations in gene expression compared to DNA methylation or histone modifications. However, LNC-RNAs appear to be more stable in the cells than the other RNA species. Moreover, there is increasing literature which clearly suggests that a single specific LNC-RNA can regulate multiple mechanisms and disease phenotypes. With specific focus on cardiovascular diseases, here we attempt to provide UpToDate information on the functional role of miRNAs and LNC-RNAs. Here we discuss the role of these epigenetic mediators in different components of cardiovascular disease which include physiopathological heart development, athersclerosis, retenosis, diabetic hearts, myocardial infarction, ischemia-reperfusion, heart valve disease, aortic aneurysm, osteogenesis, angiogenesis and hypoxia in the heart. While there is abundant literature support that shows the involvement of many LNC-RNAs and miRNAs in cardiovascular diseases, very few RNA species have been identified which regulate epigenetic mechanisms which is the current focus in this article. Understanding the role of these RNA species in regulating epigenetic mechanisms in different cell types causing cardiovascular disease, would advance the field and promote disease prevention approaches that are aimed to target epigenetic mechanisms.

Biomechanical Forces and Oxidative Stress: Implications for Pulmonary Vascular Disease

Significance: Oxidative stress in the cell is characterized by excessive generation of reactive oxygen species (ROS). Superoxide (O₂^-) and hydrogen peroxide (H₂O₂) are the main ROS involved in the regulation of cellular metabolism. As our fundamental understanding of the underlying causes of lung disease has increased it has become evident that oxidative stress plays a critical role. Recent Advances: A number of cells in the lung both produce, and respond to, ROS. These include vascular endothelial and smooth muscle cells, fibroblasts, and epithelial cells as well as the cells involved in the inflammatory response, including macrophages, neutrophils, eosinophils. The redox system is involved in multiple aspects of cell metabolism and cell homeostasis. Critical Issues: Dysregulation of the cellular redox system has consequential effects on cell signaling pathways that are intimately involved in disease progression. The lung is exposed to biomechanical forces (fluid shear stress, cyclic stretch, and pressure) due to the passage of blood through the pulmonary vessels and the distension of the lungs during the breathing cycle. Cells within the lung respond to these forces by activating signal transduction pathways that alter their redox state with both physiologic and pathologic consequences. Future Directions: Here, we will discuss the intimate relationship between biomechanical forces and redox signaling and its role in the development of pulmonary disease. An understanding of the molecular mechanisms induced by biomechanical forces in the pulmonary vasculature is necessary for the development of new therapeutic strategies.

Involvement of Epigenetic Mechanisms and Non-coding RNAs in Blood-Brain Barrier and Neurovascular Unit Injury and Recovery After Stroke

Cessation of blood flow leads to a complex cascade of pathophysiological events at the blood-vascular-parenchymal interface which evolves over time and space, and results in damage to neural cells and edema formation. Cerebral ischemic injury evokes a profound and deleterious upregulation in inflammation and triggers multiple cell death pathways, but it also induces a series of the events associated with regenerative responses, including vascular remodeling, angiogenesis, and neurogenesis. Emerging evidence suggests that epigenetic reprograming could play a pivotal role in ongoing post-stroke neurovascular unit (NVU) changes and recovery. This review summarizes current knowledge about post-stroke recovery processes at the NVU, as well as epigenetic mechanisms and modifiers (e.g., DNA methylation, histone modifying enzymes and microRNAs) associated with stroke injury, and NVU repair. It also discusses novel drug targets and therapeutic strategies for enhancing post-stroke recovery.

Therapeutic targets for endothelial dysfunction in vascular diseases

Vascular endothelial cells are located on the surface of the blood vessels. It has been recognized as an important barrier to the regulation of vascular homeostasis by regulating the blood flow of micro- or macrovascular vessels. Indeed, endothelial dysfunction is an initial stage of vascular diseases and is an important prognostic indicator of cardiovascular and metabolic diseases such as atherosclerosis, hypertension, heart failure, or diabetes. Therefore, in order to develop therapeutic targets for vascular diseases, it is important to understand the key factors involved in maintaining endothelial function and the signaling pathways affecting endothelial dysfunction. The purpose of this review is to describe the function and underlying signaling pathway of oxidative stress, inflammatory factors, shear stress, and epigenetic factors in endothelial dysfunction, and introduce recent therapeutic targets for the treatment of cardiovascular diseases.

Atherosclerosis and flow: roles of epigenetic modulation in vascular endothelium

Background

Endothelial cell (EC) dysfunctions, including turnover enrichment, gap junction disruption, inflammation, and oxidation, play vital roles in the initiation of vascular disorders and atherosclerosis. Hemodynamic forces, i.e., atherprotective pulsatile (PS) and pro-atherogenic oscillatory shear stress (OS), can activate mechanotransduction to modulate EC function and dysfunction. This review summarizes current studies aiming to elucidate the roles of epigenetic factors, i.e., histone deacetylases (HDACs), non-coding RNAs, and DNA methyltransferases (DNMTs), in mechanotransduction to modulate hemodynamics-regulated EC function and dysfunction.

Main body of the abstract

OS enhances the expression and nuclear accumulation of class I and class II HDACs to induce EC dysfunction, i.e., proliferation, oxidation, and inflammation, whereas PS induces phosphorylation-dependent nuclear export of class II HDACs to inhibit EC dysfunction. PS induces overexpression of the class III HDAC Sirt1 to enhance nitric oxide (NO) production and prevent EC dysfunction. In addition, hemodynamic forces modulate the expression and acetylation of transcription factors, i.e., retinoic acid receptor α and krüppel-like factor-2, to transcriptionally regulate the expression of microRNAs (miRs). OS-modulated miRs, which stimulate proliferative, pro-inflammatory, and oxidative signaling, promote EC dysfunction, whereas PS-regulated miRs, which induce anti-proliferative, anti-inflammatory, and anti-oxidative signaling, inhibit EC dysfunction. PS also modulates the expression of long non-coding RNAs to influence EC function. i.e., turnover, aligmant, and migration. On the other hand, OS enhances the expression of DNMT-1 and -3a to induce EC dysfunction, i.e., proliferation, inflammation, and NO repression.

Conclusion

Overall, epigenetic factors play vital roles in modulating hemodynamic-directed EC dysfunction and vascular disorders, i.e., atherosclerosis. Understanding the detailed mechanisms through which epigenetic factors regulate hemodynamics-directed EC dysfunction and vascular disorders can help us to elucidate the pathogenic mechanisms of atherosclerosis and develop potential therapeutic strategies for atherosclerosis treatment.

Role of flow-sensitive microRNAs and long noncoding RNAs in vascular dysfunction and atherosclerosis

Atherosclerosis is the primary underlying cause of myocardial infarction, ischemic stroke, and peripheral artery disease. The disease preferentially occurs in arterial regions exposed to disturbed blood flow, in part, by altering expression of flow-sensitive coding- and non-coding genes. In this review, we summarize the role of noncoding RNAs, [microRNAs (miRNAs) and long noncoding RNAs(lncRNAs)], as regulators of gene expression and outline their relationship to the pathogenesis of atherosclerosis. While miRNAs are small noncoding genes that post-transcriptionally regulate gene expression by targeting mRNA transcripts, the lncRNAs regulate gene expression by diverse mechanisms, which are still emerging and incompletely understood. We focused on multiple flow-sensitive miRNAs such as, miR-10a, -19a, -23b, -17~92, -21, -663, -92a, -143/145, -101, -126, -712, -205, and -155 that play a critical role in endothelial function and atherosclerosis by targeting inflammation, cell cycle, proliferation, migration, apoptosis, and nitric oxide signaling. Flow-dependent regulation of lncRNAs is just emerging, and their role in vascular dysfunction and atherosclerosis is unknown. Here, we discuss the flow-sensitive lncRNA STEEL along with other lncRNAs studied in the context of vascular pathophysiology and atherosclerosis such as MALAT1, MIAT1, ANRIL, MYOSLID, MEG3, SENCR, SMILR, LISPR1, and H19. Also discussed is the use of these noncoding RNAs as potential biomarkers and therapeutics to reduce and regress atherosclerosis.

Endothelial Cell Mechanotransduction in the Dynamic Vascular Environment

The vascular endothelial cells (ECs) that line the inner layer of blood vessels are responsible for maintaining vascular homeostasis under physiological conditions. In the presence of disease or injury, ECs can become dysfunctional and contribute to a progressive decline in vascular health. ECs are constantly exposed to a variety of dynamic mechanical stimuli, including hemodynamic shear stress, pulsatile stretch, and passive signaling cues derived from the extracellular matrix. This review describes the molecular mechanisms by which ECs perceive and interpret these mechanical signals. The translational applications of mechanosensing are then discussed in the context of endothelial-to-mesenchymal transition and engineering of vascular grafts.

Downregulation of GATA6 in mTOR-inhibited human aortic endothelial cells: effects on TNF-α-induced VCAM-1 expression and monocytic cell adhesion

Increased expression of vascular cell adhesion molecule 1 (VCAM-1) on the aortic endothelium is an early marker of atherogenesis, promoted in part by elevated levels of inflammatory cytokines such as TNF-α. Mammalian target of rapamycin (mTOR) is a ubiquitous signaling molecule that has been considered to contribute to diverse cellular processes through mTOR complex 1 (mTORC1) or complex 2 (mTORC2). This study aimed to elucidate the role of mTOR signaling in TNF-α-induced VCAM-1 expression by the arterial endothelium. Primary human aortic endothelial cells (HAECs) were treated with low-dose (0.1 ng/ml) TNF-α, and VCAM-1 expression was measured by real-time quantitative PCR, Western blot analysis, and flow cytometry. Inhibition of mTOR through siRNA-mediated depletion or treatment with chemical inhibitors rapamycin or torin 1 suppressed VCAM1 transcription, which translated to inhibition of VCAM-1 surface expression by HAECs and concomitant decreased adhesion of monocytes. A promoter luciferase assay and chromatin immunoprecipitation indicated that mTOR regulated VCAM1 transcription through a mechanism involving transcription factor GATA6. Activation of PKC-α and an increase in miR-200a-3p expression, caused by mTOR inhibition but not disruption of mTORC1 or mTORC2 singly or together, decreased TNF-α-induced GATA6 expression and its enrichment at the VCAM1 promoter. In conclusion, mTOR inhibition activates PKC-α independently of disruption of mTORC1 and/or mTORC2, which challenges the conventional wisdom regarding mTOR signaling. Moreover, mTOR signals through transcriptional and posttranscriptional mechanisms to elicit maximal cytokine-induced endothelial inflammation that precedes atherosclerosis. NEW & NOTEWORTHY Both mammalian target of rapamycin (mTOR) complex 1 (mTORC1) and mTORC2 contribute to PKC-α activation in the human aortic endothelium. Inhibition of mTOR is not equivalent to disruption of mTORC1 and/or mTORC2 in affecting human aortic endothelial cell signaling. Specifically, inhibition of mTOR causes PKC-α activation and miR-200a-3p upregulation, which independently suppresses TNF-α-induced transcription factor GATA6 expression and subsequently inhibits VCAM-1 expression and monocytic cell adhesion onto the aortic endothelium.

Hemodynamics-Based Strategy of Using Retinoic Acid Receptor and Retinoid X Receptor Agonists to Induce MicroRNA-10a and Inhibit Atherosclerotic Lesion

The protocols in this chapter describe methods for identifying the functional roles of retinoic acid receptor (RAR) and retinoid X receptor (RXR) signaling in atherosclerosis and developing RARα/RXRα-specific agonists as hemodynamics-based therapeutic components for atherosclerosis treatment. In vitro cell culture flow system is used to elucidate the effects of different flow patterns and shear stresses, i.e., atherogenic oscillatory shear stress (OS) vs. atheroprotective pulsatile shear stress (PS), on RAR/RXR signaling and inflammatory responses in vascular endothelial cells (ECs). Western blotting, nuclear and cytoplasmic protein extraction, immunoprecipitation, and in situ proximity ligation assay are used to examine the expression, location, and association of RARs (i.e., RARα, RARβ, and RARγ) and RXRs (i.e., RXRα, RXRβ, and RXRγ) in ECs in response to OS vs. PS. Chromatin immunoprecipitation is used to examine the binding activity of RARα/RA-responsive elements (RARE). RT-microRNA (miR) quantitative real-time PCR and RT-PCR are used to detect the expressions of miR-10a and pro-inflammatory molecules, respectively. Specific siRNAs of RARα and RXRα, precursor miR-10a (PreR-10a), and antagomiR-10a (AMR-10a) are used to elucidate the regulatory roles of RARα, RXRα, and miR-10a in pro-inflammatory signaling in ECs. RARα/RXRα-specific agonists are used to induce miR-10a expression and inhibit OS-induced pro-inflammatory signaling in ECs in vitro. Apolipoprotein E-deficient (ApoE^-/-) mice are used as an atherosclerotic animal model. Administration of ApoE^-/- mice with RARα/RXRα-specific agonists results in inhibitions in atherosclerotic lesion formation. Co-administration of ApoE^-/- mice with RARα/RXRα agonists and AMR-10a is performed to identify the role of miR-10a in RARα/RXRα agonists-mediated inhibition in atherosclerotic lesions. Oil Red O staining and H&E staining are used to examine the levels of atherosclerotic lesions in the vessel wall. In situ miR hybridization and immunohistochemical staining are used to detect the expression of miR-10a and pro-inflammatory molecules and the infiltration of inflammatory cells in the vessel wall. RARα/RXRα-specific agonists are used to mimic the atheroprotective effects of PS to induce endothelial miR-10a and hence repress OS-induced pro-inflammatory signaling and atherosclerotic lesion formation in vivo. The results indicate that RAR/RXR-specific agonists have great potential to be developed as hemodynamics-based therapeutic components for atherosclerosis treatment.

Identification and differential regulation of microRNAs during thyroid hormone-dependent metamorphosis in Microhyla fissipes

BACKGROUND

Anuran metamorphosis, which is obligatorily initiated and sustained by thyroid hormone (TH), is a dramatic example of extensive morphological, biochemical and cellular changes occurring during post-embryonic development. Thus, it provides an ideal model to understand the actions of the hormone and molecular mechanisms underlying these developmental and apoptotic processes. In addition to transcriptional factors, microRNAs (miRNAs) play key roles in diverse biological processes via post-transcriptional repression of mRNAs. However, the possible role of miRNAs in anuran metamorphosis is not well understood. Screening and identification of TH-responding miRNAs are required to reveal the integrated regulatory mechanisms of TH during metamorphosis. Given the specific role of TRs during M. fissipes metamorphosis and the characteristics of M. fissipes as an ideal model, Illumina sequencing technology was employed to get a full scope of miRNA in M. fissipes metamorphosis treated by T3.

RESULTS

Morphological and histological analysis revealed that 24 h T3 treatment M. fissipes tadpoles resembled that at the climax of natural metamorphosis. Thus, small RNA libraries were constructed from control and 24 h T3 treatment groups. A total of 164 conserved miRNAs and 36 predicted novel miRNAs were characterized. Furthermore, 5' first and ninth nucleotides of miRNAs were significantly enriched in U in our study. In all, 21 miRNAs were differentially expressed between the T3 and control groups (p < 0.01). A total of 10,206 unigenes were identified as target genes of these differentially expressed miRNAs. KEGG pathway analysis indicated that the most overrepresented miRNA target genes were enriched in the "PI3k-Akt signaling pathway". In addition, a network associated with the TH signaling pathway provides an opportunity to further understand the complex biological processes that occur in metamorphosis.

CONCLUSIONS

We identified a large number of miRNAs during M. fissipes metamorphosis, and 21 of them were differentially expressed in the two groups that represented two different metamorphic stages. These miRNAs may play important roles during metamorphosis. The study gives us clues for further studies of the mechanisms of anuran metamorphosis and provides a model to study the mechanism of TH-affected biological processes in humans.

Differential expression profile of long non-coding RNAs in human thoracic aortic aneurysm

Thoracic aortic aneurysm (TAA) is progressive fatal aortic pathological dilation, which is characterized by increased proteoglycans and loss of elastic fibers. Recent advances in long non-coding RNAs (lncRNAs), an important regulator in many biological processes, suggested the close correlation between expression patterns and disease progression. In the present study, the ascending aortic tissues were collected from ascending TAA patients (n = 33) and organ donors (n = 16). Microarray analysis and real-time PCR were then applied to detect the lncRNA expression profiles. A total of 147 differentially expressed lncRNAs were determined, including 104 upregulated and 43 downregulated lncRNAs. Bioinformatics analysis showed 51.7% of differentially expressed lncRNAs were sense-overlapping, and most of the down-regulated lncRNAs were located on chromosome 1, 7, and 12. Subgroup analysis of TAA patients indicated that the expression of lnc-HLTF-5 was significantly higher in hypertension group than non-hypertension group (P < 0.05). Spearman correlation analysis further confirmed that the lnc-HLTF-5 level was positively correlated with the expanded ascending aortic diameter (r_s  = 0.483, P = 0.004) and MMP9 level (r_s  = 0.465, P = 0.006). Our results expanded the lncRNA expression patterns in aortic disease, and provided experimental basis for future investigation on TAA pathogenesis.

miR-10a-5p, miR-99a-5p and miR-21-5p are steroid-responsive circulating microRNAs

Steroid-induced osteonecrosis of the femoral head (ONFH) is a common orthopedic disease. The lack of specific manifestations and effective diagnostic methods make it difficult for this disease to be diagnosed at early stages. Recent studies have shown that microRNAs (miRNA) participate in the development of steroid-induced ONFH, but there is limited research into the diagnostic use of circulating miRNAs. Blood samples from 23 human subjects (7 systemic lupus erythematosus (SLE) patients with steroid-induced ONFH; 7 SLE controls without ONFH; and 9 healthy controls) and 71 rats (19 with steroid-induced ONFH; 28 receiving steroids without ONFH; and 24 untreated controls) were collected to verify the abundance of changes of 6 previously identified ONFH-associated plasma miRNAs (miR-423-5p, miR-99a-5p, miR-10a-5p, miR-21-5p, miR-130a-3p and miR-6787-5p) by quantitative RT-PCR (Reverse Transcription-Polymerase Chain Reaction). In humans, the circulating levels of miR-10a-5p, miR-99a-5p and miR-21-5p were increased in SLE patients treated with cortico steroid regardless of ONFH status when compared with healthy controls. However, miR-423-5p, miR-6787-5p and miR-130a-3p showed no significant differences between the three groups. In the rat model, the success rate of steroid-induced ONFH was 40.4% (19/47) based on pathological examination and confirmation by micro-CT scan. Similar to human plasma, the circulating levels of miR-10a-5p, miR-99a-5p and miR-21-5p were increased in steroid-treated rats independent of ONFH development. The serum levels of miR-10a-5p, miR-99a-5p and miR-21-5p were increased by steroid treatment regardless of ONFH development in both humans and rats. These data suggested that miR-10a-5p, miR-99a-5p and miR-21-5p are steroid-responsive circulating miRNAs, but they are not specific for diagnosing steroid-induced ONFH.

Endothelial microRNAs regulating the NF-κB pathway and cell adhesion molecules during inflammation

The surface of endothelial cells is covered with cell adhesion molecules, including E-selectin, intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM- 1) , that mediate the adhesion and extravasation of leukocytes and play pivotal roles in inflammatory response. microRNAs (miRNAs) regulate the expression of these important cell adhesion molecules through two distinct major mechanisms, namely via modulating the proinflammatory NF-κB pathway, which controls their transcription, and via directly targeting them. The present review highlights the role of various miRNAs in controlling the expression of E-selectin, ICAM-1, and VCAM-1: a type of regulation that can be harnessed for therapeutic prevention of inflammation-associated diseases such as atherosclerosis and sepsis. The roles of secreted miRNAs as paracrine regulators, and cell adhesion molecule-based miRNA delivery are also addressed.-Zhong, L., Simard, M. J., Huot, J. Endothelial microRNAs regulating the NF-κB pathway and cell adhesion molecules during inflammation.

Induction of microRNA-10a using retinoic acid receptor-α and retinoid x receptor-α agonists inhibits atherosclerotic lesion formation

BACKGROUND AND AIMS

MicroRNA (miR)-10a is a shear-regulated miR with the lowest expression in vascular endothelial cells (ECs) in athero-susceptible regions with oscillatory shear stress (OS). The aim of this study is to elucidate the relationship between EC miR-10a and atherosclerosis and develop a hemodynamics-based strategy for atherosclerosis treatment.

METHODS

A combination of in vitro flow system and in vivo experimental animals was used to examine the functional roles of EC miR-10a and its clinical applications in atherosclerosis.

RESULTS

En face staining showed that EC miR-10a is down-regulated in the inner curvature (OS region) of aortic arch in rats. Co-administration with retinoic acid receptor-α (RARα)- and retinoid X receptor-α (RXRα)-specific agonists rescued EC miR-10a expression in this OS region. These effects of OS and RARα/RXRα-specific agonists on EC miR-10a expression were confirmed by the in vitro flow system, and were modulated by the RARα-histone deacetylases complex, with the consequent modulation in the downstream GATA6/vascular cell adhesion molecule (VCAM)-1 signaling cascade. Animal studies showed that miR-10a levels are decreased in both aortic endothelium of atherosclerotic lesions and blood plasma from apolipoprotein E-deficient (ApoE^-/-) mice. In vivo induction of EC miR-10a by administration of RARα/RXRα-specific agonists protects ApoE^-/- mice from atherosclerosis through inhibition of GATA6/VCAM-1 signaling and inflammatory cell infiltration.

CONCLUSIONS

Our findings indicate that down-regulation of miR-10a in aortic endothelium and blood serum is associated with atherosclerosis, and miR-10a has potential to be developed as diagnostic molecule for atherosclerosis. Moreover, EC miR-10a induction by RARα/RXRα-specific agonists is a potential hemodynamics-based strategy for atherosclerosis treatment.

Cardiovascular Risk Factors and Markers

Cardiovascular risk is assessed for the prediction and appropriate management of patients using collections of identified risk markers obtained from clinical questionnaire information, concentrations of certain blood molecules (e.g., N-terminal proB-type natriuretic peptide fragment and soluble receptors of tumor-necrosis factor-α and interleukin-2), imaging data using various modalities, and electrocardiographic variables, in addition to traditional risk factors.

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.

The Mammalian Target of Rapamycin and DNA methyltransferase 1 axis mediates vascular endothelial dysfunction in response to disturbed flow

The earliest atherosclerotic lesions preferentially develop in arterial regions experienced disturbed blood flow, which induces endothelial expression of pro-atherogenic genes and the subsequent endothelial dysfunction. Our previous study has demonstrated an up-regulation of DNA methyltransferase 1 (DNMT1) and a global hypermethylation in vascular endothelium subjected to disturbed flow. Here, we determined that DNMT1-specific inhibition in arterial wall ameliorates the disturbed flow-induced atherosclerosis through, at least in part, targeting cell cycle regulator cyclin A and connective tissue growth factor (CTGF). We identified the signaling pathways mediating the flow-induction of DNMT1. Inhibition of the mammalian target of rapamycin (mTOR) suppressed the DNMT1 up-regulation both in vitro and in vivo. Together, our results demonstrate that disturbed flow influences endothelial function and induces atherosclerosis in an mTOR/DNMT1-dependent manner. The conclusions obtained from this study might facilitate further evaluation of the epigenetic regulation of endothelial function during the pathological development of atherosclerosis and offer novel prevention and therapeutic targets of this disease.