Notch activation induces endothelial cell senescence and pro-inflammatory response: implication of Notch signaling in atherosclerosis

The Multifaceted Role of Endothelial Sirt1 in Vascular Aging: An Update

NAD+-dependent deacetylase sirtuin-1 (Sirt1) belongs to the sirtuins family, known to be longevity regulators, and exerts a key role in the prevention of vascular aging. By aging, the expression levels of Sirt1 decline with a severe impact on vascular function, such as the rise of endothelial dysfunction, which in turn promotes the development of cardiovascular diseases. In this context, the impact of Sirt1 activity in preventing endothelial senescence is particularly important. Given the key role of Sirt1 in counteracting endothelial senescence, great efforts have been made to deepen the knowledge about the intricate cross-talks and interactions of Sirt1 with other molecules, in order to set up possible strategies to boost Sirt1 activity to prevent or treat vascular aging. The aim of this review is to provide a proper background on the regulation and function of Sirt1 in the vascular endothelium and to discuss the recent advances regarding the therapeutic strategies of targeting Sirt1 to counteract vascular aging.

Vascular Aging and Atherosclerosis: A Perspective on Aging

Vascular aging (VA) is recognized as a pivotal factor in the development and progression of atherosclerosis (AS). Although various epidemiological and clinical research has demonstrated an intimate connection between aging and AS, the candidate mechanisms still require thorough examination. This review adopts an aging-centric perspective to deepen the comprehension of the intricate relationship between biological aging, vascular cell senescence, and AS. Various aging-related physiological factors influence the physical system's reactions, including oxygen radicals, inflammation, lipids, angiotensin II, mechanical forces, glucose levels, and insulin resistance. These factors cause endothelial dysfunction, barrier damage, sclerosis, and inflammation for VA and promote AS via distinct or shared pathways. Furthermore, the increase of senescent cells inside the vascular tissues, caused by genetic damage, dysregulation, secretome changes, and epigenetic modifications, might be the primary cause of VA.

New Dawn for Atherosclerosis: Vascular Endothelial Cell Senescence and Death

Endothelial cells (ECs) form the inner linings of blood vessels, and are directly exposed to endogenous hazard signals and metabolites in the circulatory system. The senescence and death of ECs are not only adverse outcomes, but also causal contributors to endothelial dysfunction, an early risk marker of atherosclerosis. The pathophysiological process of EC senescence involves both structural and functional changes and has been linked to various factors, including oxidative stress, dysregulated cell cycle, hyperuricemia, vascular inflammation, and aberrant metabolite sensing and signaling. Multiple forms of EC death have been documented in atherosclerosis, including autophagic cell death, apoptosis, pyroptosis, NETosis, necroptosis, and ferroptosis. Despite this, the molecular mechanisms underlying EC senescence or death in atherogenesis are not fully understood. To provide a comprehensive update on the subject, this review examines the historic and latest findings on the molecular mechanisms and functional alterations associated with EC senescence and death in different stages of atherosclerosis.

Atherosclerotic plaque vulnerability quantification system for clinical and biological interpretability

Acute myocardial infarction dominates coronary artery disease mortality. Identifying bio-signatures for plaque destabilization and rupture is important for preventing the transition from coronary stability to instability and the occurrence of thrombosis events. This computational systems biology study enrolled 2,235 samples from 22 independent bulks cohorts and 14 samples from two single-cell cohorts. A machine-learning integrative program containing nine learners was developed to generate a warning classifier linked to atherosclerotic plaque vulnerability signature (APVS). The classifier displays the reliable performance and robustness for distinguishing ST-elevation myocardial infarction from chronic coronary syndrome at presentation, and revealed higher accuracy to 33 pathogenic biomarkers. We also developed an APVS-based quantification system (APVSLevel) for comprehensively quantifying atherosclerotic plaque vulnerability, empowering early-warning capabilities, and accurate assessment of atherosclerosis severity. It unraveled the multidimensional dysregulated mechanisms at high resolution. This study provides a potential tool for macro-level differential diagnosis and evaluation of subtle genetic pathological changes in atherosclerosis.

N6-methylation of RNA-bound adenosine regulator HNRNPC promotes vascular endothelial dysfunction in type 2 diabetes mellitus by activating the PSEN1-mediated Notch pathway

AIM

The regulatory mechanism of m6A regulators in vascular endothelial function of type 2 diabetes mellitus (T2DM) remains largely unknown. We addressed this issue based on the data retrieved Gene Expression Omnibus (GEO) database and experimental validations.

METHODS

Expression of m6A methylation regulators was evaluated in T2DM samples of GSE76894 dataset and GSE156341 dataset. Further analysis of candidate m6A methylation regulators was conducted in the thoracic aorta of db/db mice and high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs). Ectopic expression and depletion experiments were conducted to detect effects of m6A methylation regulators on vascular endothelial function in T2DM.

RESULTS

It emerged that three m6A methylation regulators (HNRNPC, RBM15B, and ZC3H13) were highly expressed in T2DM, which were related to vascular EC function, showing diagnostic values for T2DM. HNRNPC expression in the thoracic aorta of db/db mice was higher than that in heterozygous db mice, and HNRNPC expression in HG-induced HUVECs was upregulated when compared with normal glucose-exposed HUVECs. Furthermore, HNRNPC activated PSEN1-dependent Notch pathway to induce eNOS inactivation and NO production decrease, thereby causing vascular endothelial dysfunction in T2DM.

CONCLUSIONS

HNRNPC impaired vascular endothelial function to enhance the development of vascular complications in T2DM through PSEN1-mediated Notch signaling pathway.

Notch Signaling in Acute Inflammation and Sepsis

Notch signaling, a highly conserved pathway in mammals, is crucial for differentiation and homeostasis of immune cells. Besides, this pathway is also directly involved in the transmission of immune signals. Notch signaling per se does not have a clear pro- or anti-inflammatory effect, but rather its impact is highly dependent on the immune cell type and the cellular environment, modulating several inflammatory conditions including sepsis, and therefore significantly impacts the course of disease. In this review, we will discuss the contribution of Notch signaling on the clinical picture of systemic inflammatory diseases, especially sepsis. Specifically, we will review its role during immune cell development and its contribution to the modulation of organ-specific immune responses. Finally, we will evaluate to what extent manipulation of the Notch signaling pathway could be a future therapeutic strategy.

Notch Signaling in the Vasculature: Angiogenesis and Angiocrine Functions

Formation of a functional blood vessel network is a complex process tightly controlled by pro- and antiangiogenic signals released within the local microenvironment or delivered through the bloodstream. Endothelial cells precisely integrate such temporal and spatial changes in extracellular signals and generate an orchestrated response by modulating signaling transduction, gene expression, and metabolism. A key regulator in vessel formation is Notch signaling, which controls endothelial cell specification, proliferation, migration, adhesion, and arteriovenous differentiation. This review summarizes the molecular biology of endothelial Notch signaling and how it controls angiogenesis and maintenance of the established, quiescent vasculature. In addition, recent progress in the understanding of Notch signaling in endothelial cells for controlling organ homeostasis by transcriptional regulation of angiocrine factors and its relevance to disease will be discussed.

Regulation of Notch Signaling Pathway to Innate Lymphoid Cells in Patients with Acute Myocardial Infarction

The Notch signaling pathway is an important regulator in fate decisions and immune responses of innate lymphoid cells (ILCs). However, the function of Notch signaling in ILCs in acute coronary syndrome is still not fully elucidated. Thirty-one unstable angina pectoris (UAP) patients, 21 acute myocardial infarction (AMI) patients, and 20 controls were included in this study. Peripheral blood mononuclear cells (PBMCs) were isolated. The mRNA expression levels of Notch receptors and ligands were measured by real-time PCR, while ILC subsets were measured by flow cytometry. Lin^- cells were purified and stimulated with γ-secretase inhibitor (GSI). ILC subsets, transcription factors, and secreted cytokines were assessed. Notch receptor and ligand mRNA levels were elevated in PBMCs and peripheral lin^- cells from AMI patients. There was no significant difference in total lin^-CD45⁺CD161⁺CD127⁺ ILC frequency among three groups. The CRTH2^-CD117^- ILC1 subset was down-regulated, while the CRTH2⁺ ILC2 subset was up-regulated in AMI patients. The CRTH2^-CD117⁺ ILC3 subpopulation was comparable among the three groups. ILC1% was negatively correlated with Notch1 and Notch2 in AMI patients. Inhibition of Notch signaling pathway by GSI induced elevations in ILC1 frequency, T-bet mRNA expression, and interferon-γ secretion and reduced ILC2 frequency, GATA3 mRNA levels, and interleukin-5/interleukin-13 production by lin^- cells from AMI patients. The current data indicated that activation of Notch signaling pathway might contribute to ILC1-to-ILC2 shift in peripheral blood in AMI patients.

Mechanisms and consequences of endothelial cell senescence

Endothelial cells are located at the crucial interface between circulating blood and semi-solid tissues and have many important roles in maintaining systemic physiological function. The vascular endothelium is particularly susceptible to pathogenic stimuli that activate tumour suppressor pathways leading to cellular senescence. We now understand that senescent endothelial cells are highly active, secretory and pro-inflammatory, and have an aberrant morphological phenotype. Moreover, endothelial senescence has been identified as an important contributor to various cardiovascular and metabolic diseases. In this Review, we discuss the consequences of endothelial cell exposure to damaging stimuli (haemodynamic forces and circulating and endothelial-derived factors) and the cellular and molecular mechanisms that induce endothelial cell senescence. We also discuss how endothelial cell senescence causes arterial dysfunction and contributes to clinical cardiovascular diseases and metabolic disorders. Finally, we summarize the latest evidence on the effect of eliminating senescent endothelial cells (senolysis) and identify important remaining questions to be addressed in future studies.

JAG1-NOTCH4 mechanosensing drives atherosclerosis

Endothelial cell (EC) sensing of disturbed blood flow triggers atherosclerosis, a disease of arteries that causes heart attack and stroke, through poorly defined mechanisms. The Notch pathway plays a central role in blood vessel growth and homeostasis, but its potential role in sensing of disturbed flow has not been previously studied. Here, we show using porcine and murine arteries and cultured human coronary artery EC that disturbed flow activates the JAG1-NOTCH4 signaling pathway. Light-sheet imaging revealed enrichment of JAG1 and NOTCH4 in EC of atherosclerotic plaques, and EC-specific genetic deletion of Jag1 (Jag1ECKO) demonstrated that Jag1 promotes atherosclerosis at sites of disturbed flow. Mechanistically, single-cell RNA sequencing in Jag1ECKO mice demonstrated that Jag1 suppresses subsets of ECs that proliferate and migrate. We conclude that JAG1-NOTCH4 sensing of disturbed flow enhances atherosclerosis susceptibility by regulating EC heterogeneity and that therapeutic targeting of this pathway may treat atherosclerosis.

Cd248a and Cd248b in zebrafish participate in innate immune responses

CD248, also known as endosialin or tumor endothelial marker 1, is a type I single transmembrane glycoprotein. CD248 has been demonstrated to be upregulated in cancers, tumors and many fibrotic diseases in human and mice, such as liver damage, pulmonary fibrosis, renal fibrosis, arthritis and tumor neovascularization. However, no definite CD248 orthologs in fish have been documented so far. In this study, we report the identification of cd248a and cd248b in the zebrafish. Both the phylogenetic analysis and the conserved synteny strongly suggested that zebrafish cd248a and cd248b are orthologs of the human CD248. Both cd248a and cd248b exhibited similar and dynamic expression pattern in early development, both genes had weak maternal expression, the zygotic transcripts were first seen in anterior somites and head mesenchyme, then shifted to eyes and head mesenchyme, later expanded to branchial arches, and gradually declined with development. The expression profiles of cd248a and cd248b were upregulated upon LPS (Lipopolysaccharide) challenge. Both Cd248a protein and Cd248b protein were localized on the cell membrane and cytoplasm, and overexpression of cd248a and cd248b induced the expression of pro-inflammatory cytokines, in vitro and in vivo. Moreover, deficiency of cd248a or cd248b both downregulated the expression of pro-inflammatory cytokines and upregulated anti-inflammatory cytokine. Additionally, loss of cd248a or cd248b both downregulated the expression of pro-inflammatory cytokines after LPS treatment. Taken together, these results indicated that cd248a and cd248b in zebrafish were involved in immune response and would provide further information to understand functions of Cd248 protein in innate immunity of fish.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

hsa-miR-518-5p/hsa-miR-3135b Regulates the REL/SOD2 Pathway in Ischemic Cerebral Infarction

Objectives

Ischemic cerebral infarction (ICI) is a fatal neurovascular disorder. A bioinformatics approach based on single-cell and bulk RNA-seq analyses was applied to investigate the pathways and genes involved in ICI and study the expression profile of these genes.

Methods

First, the aberrantly regulated “small-molecule ribonucleic acids” [microRNA (miRNAs)] and messenger RNAs (mRNAs) were analyzed using transcriptome data from the ischemic brain infarction dataset of the Gene Expression Omnibus (GEO) database. In mouse cerebrovascular monocytes, the single-cell regulatory network inference and clustering (SCENIC) workflow was used to identify key transcription factors (TFs). Then, the two miRNA-TF-mRNA interaction networks were constructed. Moreover, the molecular complex detection (MCODE) extracted the core sub-networks and identified the important TFs within these sub-networks. Finally, whole blood samples were collected for validation of the expression of critical molecules in ICI.

Results

We identified four cell types and 266 regulons in mouse cerebrovascular monocytes using SCENIC analysis. Moreover, 112 differently expressed miRNAs and 3,780 differentially expressed mRNAs were identified. We discovered potential biomarkers in ICI by building a miRNA-TF-mRNA interaction network. The hsa-miR-518-5p/hsa-miR-3135b/REL/SOD2 was found to play a potential role in ICI progression. The expression of REL and superoxide dismutase 2 (SOD2) was significantly elevated in the ICI group in the clinical cohort (P < 0.05). Furthermore, a REL expression was elevated in endothelial cells and fibroblasts at the single-cell level, indicating that REL is a cell-specific regulon. Functional enrichment analyses revealed that REL is primarily engaged in neurotransmitter activity and oxidative phosphorylation.

Conclusions

Our research uncovered novel biomarkers for ICI of neurovascular disease. The hsa-miR-518-5p/hsa-miR-3135b may regulate the REL/SOD2 pathway in ICI progression.

Monocytes augment inflammatory responses in human aortic valve interstitial cells via β2-integrin/ICAM-1-mediated signaling

OBJECTIVE

Inflammatory infiltration in aortic valves promotes calcific aortic valve disease (CAVD) progression. While soluble extracellular matrix (ECM) proteins induce inflammatory responses in aortic valve interstitial cells (AVICs), the impact of monocytes on AVIC inflammatory responses is unknown. We tested the hypothesis that monocytes enhance AVIC inflammatory responses to soluble ECM protein in this study.

METHODS

Human AVICs isolated from normal aortic valves were cocultured with monocytes and stimulated with soluble ECM protein (matrilin-2). ICAM-1 and IL-6 productions were assessed. YAP and NF-κB phosphorylation were analyzed. Recombinant CD18, neutralizing antibodies against β₂-integrin or ICAM-1, and inhibitor of YAP or NF-κB were applied.

RESULTS

AVIC expression of ICAM-1 and IL-6 was markedly enhanced by the presence of monocytes, although matrilin-2 did not affect monocyte production of ICAM-1 or IL-6. Matrilin-2 up-regulated the expression of monocyte β₂-integrin and AVIC ICAM-1, leading to monocyte-AVIC adhesion. Neutralizing β₂-integrin or ICAM-1 in coculture suppressed monocyte adhesion to AVICs and the expression of ICAM-1 and IL-6. Recombinant CD18 enhanced the matrilin-2-induced ICAM-1 and IL-6 expression in AVIC monoculture. Further, stimulation of coculture with matrilin-2 induced greater YAP and NF-κB phosphorylation. Inhibiting either YAP or NF-κB markedly suppressed the inflammatory response to matrilin-2 in coculture.

CONCLUSION

Monocyte β₂-integrin interacts with AVIC ICAM-1 to augment AVIC inflammatory responses to soluble matrilin-2 through enhancing the activation of YAP and NF-κB signaling pathways. Infiltrated monocytes may promote valvular inflammation through cell-cell interaction with AVICs to enhance their sensitivity to damage-associated molecular patterns.

Notch Signaling and Cross-Talk in Hypoxia: A Candidate Pathway for High-Altitude Adaptation

Hypoxia triggers complex inter- and intracellular signals that regulate tissue oxygen (O₂) homeostasis, adjusting convective O₂ delivery and utilization (i.e., metabolism). Human populations have been exposed to high-altitude hypoxia for thousands of years and, in doing so, have undergone natural selection of multiple gene regions supporting adaptive traits. Some of the strongest selection signals identified in highland populations emanate from hypoxia-inducible factor (HIF) pathway genes. The HIF pathway is a master regulator of the cellular hypoxic response, but it is not the only regulatory pathway under positive selection. For instance, regions linked to the highly conserved Notch signaling pathway are also top targets, and this pathway is likely to play essential roles that confer hypoxia tolerance. Here, we explored the importance of the Notch pathway in mediating the cellular hypoxic response. We assessed transcriptional regulation of the Notch pathway, including close cross-talk with HIF signaling, and its involvement in the mediation of angiogenesis, cellular metabolism, inflammation, and oxidative stress, relating these functions to generational hypoxia adaptation.

Endothelial SIRT1 as a Target for the Prevention of Arterial Aging: Promises and Challenges

ABSTRACT

SIRT1, a member of the sirtuin family of longevity regulators, possesses potent activities preventing vascular aging. The expression and function of SIRT1 in endothelial cells are downregulated with age, in turn causing early vascular aging and predisposing various vascular abnormalities. Overexpression of SIRT1 in the vascular endothelium prevents aging-associated endothelial dysfunction and senescence, thus the development of hypertension and atherosclerosis. Numerous efforts have been directed to increase SIRT1 signaling as a potential strategy for different aging-associated diseases. However, the complex mechanisms underlying the regulation of SIRT1 have posed a significant challenge toward the design of specific and effective therapeutics. This review aimed to provide a summary on the regulation and function of SIRT1 in the vascular endothelium and to discuss the different approaches targeting this molecule for the prevention and treatment of age-related cardiovascular and cerebrovascular diseases.

An update on the roles of immune system-derived microRNAs in cardiovascular diseases

Cardiovascular diseases (CVD) are a leading cause of human death worldwide. Over the past two decades, the emerging field of cardioimmunology has demonstrated how cells of the immune system play vital roles in the pathogenesis of CVD. MicroRNAs (miRNAs) are critical regulators of cellular identity and function. Cell-intrinsic, as well as cell-extrinsic, roles of immune and inflammatory cell-derived miRNAs have been, and continue to be, extensively studied. Several 'immuno-miRNAs' appear to be specifically expressed or demonstrate greatly enriched expression within leucocytes. Identification of miRNAs as critical regulators of immune system signalling pathways has posed the question of whether and how targeting these molecules therapeutically, may afford opportunities for disease treatment and/or management. As the field of cardioimmunology rapidly continues to advance, this review discusses findings from recent human and murine studies which contribute to our understanding of how leucocytes of innate and adaptive immunity are regulated-and may also regulate other cell types, via the actions of the miRNAs they express, in the context of CVD. Finally, we focus on available information regarding miRNA regulation of regulatory T cells and argue that targeted manipulation of miRNA regulated pathways in these cells may hold therapeutic promise for the treatment of CVD and associated risk factors.

Dynamic alterations of H3K4me3 and H3K27me3 at ADAM17 and Jagged-1 gene promoters cause an inflammatory switch of endothelial cells

Histone protein modifications control the inflammatory state of many immune cells. However, how dynamic alteration in histone methylation causes endothelial inflammation and apoptosis is not clearly understood. To examine this, we explored two contrasting histone methylations; an activating histone H3 lysine 4 trimethylation (H3K4me3) and a repressive histone H3 lysine 27 trimethylation (H3K27me3) in endothelial cells (EC) undergoing inflammation. Through computer-aided reconstruction and 3D printing of the human coronary artery, we developed a unique model where EC were exposed to a pattern of oscillatory/disturbed flow as similar to in vivo conditions. Upon induction of endothelial inflammation, we detected a significant rise in H3K4me3 caused by an increase in the expression of SET1/COMPASS family of H3K4 methyltransferases, including MLL1, MLL2, and SET1B. In contrast, EC undergoing inflammation exhibited truncated H3K27me3 level engendered by EZH2 cytosolic translocation through threonine 367 phosphorylation and an increase in the expression of histone demethylating enzyme JMJD3 and UTX. Additionally, many SET1/COMPASS family of proteins, including MLL1 (C), MLL2, and WDR5, were associated with either UTX or JMJD3 or both and such association was elevated in EC upon exposure to inflammatory stimuli. Dynamic enrichment of H3K4me3 and loss of H3K27me3 at Notch-associated gene promoters caused ADAM17 and Jagged-1 derepression and abrupt Notch activation. Conversely, either reducing H3K4me3 or increasing H3K27me3 in EC undergoing inflammation attenuated Notch activation, endothelial inflammation, and apoptosis. Together, these findings indicate that dynamic chromatin modifications may cause an inflammatory and apoptotic switch of EC and that epigenetic reprogramming can potentially improve outcomes in endothelial inflammation-associated cardiovascular diseases.

Mechanisms of cancer stem cell senescence: Current understanding and future perspectives

Cancer stem cells (CSCs) are a small population of heterogeneous tumor cells with the capacity of self-renewal and aberrant differentiation for immortality and divergent lineages of cancer cells. In contrast to bulky tumor cells, CSCs remain less differentiated and resistant to therapy even when targeted with tissue-specific antigenic markers. This makes CSCs responsible for not only tumor initiation, development, but also tumor recurrence. Emerging evidence suggests that CSCs can undergo cell senescence, a non-proliferative state of cells in response to stress. While cell senescence attenuates tumor cell proliferation, it is commonly regarded as a tumor suppressive mechanism. However, mounting research indicates that CSC senescence also provides these cells with the capacity to evade cytotoxic effects from cancer therapy, exacerbating cancer relapse and metastasis. Recent studies demonstrate that senescence drives reprogramming of cancer cell toward stemness and promotes CSC generation. In this review, we highlight the origin, heterogeneity and senescence regulatory mechanisms of CSCs, the complex relationship between CSC senescence and tumor therapy, and the recent beneficial effects of senotherapy on eliminating senescent tumor cells.

Cellular senescence in lymphoid organs and immunosenescence

Immunosenescence is a multi-faceted phenomenon at the root of age-associated immune dysfunction. It can lead to an array of pathological conditions, including but not limited to a decreased capability to surveil and clear senescent cells (SnCs) and cancerous cells, an increased autoimmune responses leading to tissue damage, a reduced ability to tackle pathogens, and a decreased competence to illicit a robust response to vaccination. Cellular senescence is a phenomenon by which oncogene-activated, stressed or damaged cells undergo a stable cell cycle arrest. Failure to efficiently clear SnCs results in their accumulation in an organism as it ages. SnCs actively secrete a myriad of molecules, collectively called senescence-associated secretory phenotype (SASP), which are factors that cause dysfunction in the neighboring tissue. Though both cellular senescence and immunosenescence have been studied extensively and implicated in various pathologies, their relationship has not been greatly explored. In the wake of an ongoing pandemic (COVID-19) that disproportionately affects the elderly, immunosenescence as a function of age has become a topic of great importance. The goal of this review is to explore the role of cellular senescence in age-associated lymphoid organ dysfunction and immunosenescence, and provide a framework to explore therapies to rejuvenate the aged immune system.

Microtubule affinity regulating kinase 4: A promising target in the pathogenesis of atherosclerosis

Microtubule affinity regulating kinase 4 (MARK4), an important member of the serine/threonine kinase family, regulates the phosphorylation of microtubule-associated proteins and thus modulates microtubule dynamics. In human atherosclerotic lesions, the expression of MARK4 is significantly increased. Recently, accumulating evidence suggests that MARK4 exerts a proatherogenic effect via regulation of lipid metabolism (cholesterol, fatty acid, and triglyceride), inflammation, cell cycle progression and proliferation, insulin signaling, and glucose homeostasis, white adipocyte browning, and oxidative stress. In this review, we summarize the latest findings regarding the role of MARK4 in the pathogenesis of atherosclerosis to provide a rationale for future investigation and therapeutic intervention.

Targeting the Notch Signaling Pathway in Chronic Inflammatory Diseases

The Notch signaling pathway regulates developmental cell-fate decisions and has recently also been linked to inflammatory diseases. Although therapies targeting Notch signaling in inflammation in theory are attractive, their design and implementation have proven difficult, at least partly due to the broad involvement of Notch signaling in regenerative and homeostatic processes. In this review, we summarize the supporting role of Notch signaling in various inflammation-driven diseases, and highlight efforts to intervene with this pathway by targeting Notch ligands and/or receptors with distinct therapeutic strategies, including antibody designs. We discuss this in light of lessons learned from Notch targeting in cancer treatment. Finally, we elaborate on the impact of individual Notch members in inflammation, which may lay the foundation for development of therapeutic strategies in chronic inflammatory diseases.

Novel Lesional Transcriptional Signature Separates Atherosclerosis With and Without Diabetes in Yorkshire Swine and Humans

[Figure: see text].

Overexpressed miR-335-5p reduces atherosclerotic vulnerable plaque formation in acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS) may induce cardiovascular death. The correlation of mast cells related microRNAs (miRs) with risk of ACS has been investigated. We explored regulatory mechanism of miR-335-5p on macrophage innate immune response, atherosclerotic vulnerable plaque formation, and revascularization in ACS in relation to Notch signaling.

METHODS

ACS-related gene microarray was collected from Gene Expression Omnibus database. After different agomir or antagomir, or inhibitor of Notch signaling treatment, IL-6, IL-1β, TNF-α, MCP-1, ICAM-1, and VCAM-1 levels were tested in ACS mice. Additionally, Notch signaling-related genes and matrix metalloproteinases (MMPs) were measured after miR-335-5p interference. Finally, mouse atherosclerosis, lipid accumulation, and the collagen/vessel area ratio of plaque were determined.

RESULTS

miR-335-5p targeted JAG1 and mediated Notch signaling in ACS. miR-335-5p up-regulation and Notch signaling inhibition reduced expression of JAG1, Notch pathway-related genes, IL-6, IL-1β, TNF-α, MCP-1, ICAM-1, VCAM-1, and MMPs, but promote TIMP1 and TIMP2 expression. Additionally, vulnerable plaques were decreased and collagen fiber contents were observed to increase after miR-335-5p overexpression and Notch signaling inhibition.

CONCLUSIONS

Overexpression of miR-335-5p inhibited innate immune response of macrophage, reduced atherosclerotic vulnerable plaque formation, and promoted revascularization in ACS mice targeting JAG1 through Notch signaling.

Overexpressed miR-335-5p reduces atherosclerotic vulnerable plaque formation in acute coronary syndrome

BACKGROUND

Acute coronary syndrome (ACS) may induce cardiovascular death. The correlation of mast cells related microRNAs (miRs) with risk of ACS has been investigated. We explored regulatory mechanism of miR-335-5p on macrophage innate immune response, atherosclerotic vulnerable plaque formation, and revascularization in ACS in relation to Notch signaling.

METHODS

ACS-related gene microarray was collected from Gene Expression Omnibus database. After different agomir or antagomir, or inhibitor of Notch signaling treatment, IL-6, IL-1β, TNF-α, MCP-1, ICAM-1, and VCAM-1 levels were tested in ACS mice. Additionally, Notch signaling-related genes and matrix metalloproteinases (MMPs) were measured after miR-335-5p interference. Finally, mouse atherosclerosis, lipid accumulation, and the collagen/vessel area ratio of plaque were determined.

RESULTS

miR-335-5p targeted JAG1 and mediated Notch signaling in ACS. miR-335-5p up-regulation and Notch signaling inhibition reduced expression of JAG1, Notch pathway-related genes, IL-6, IL-1β, TNF-α, MCP-1, ICAM-1, VCAM-1, and MMPs, but promote TIMP1 and TIMP2 expression. Additionally, vulnerable plaques were decreased and collagen fiber contents were observed to increase after miR-335-5p overexpression and Notch signaling inhibition.

CONCLUSIONS

Overexpression of miR-335-5p inhibited innate immune response of macrophage, reduced atherosclerotic vulnerable plaque formation, and promoted revascularization in ACS mice targeting JAG1 through Notch signaling.

The aging endothelium

Cellular senescence is now recognized as one of the hallmarks of aging. Herein, we examine current findings on senescence of the vascular endothelium and its impacts on age-related vascular diseases. Endothelial senescence can result in systemic metabolic changes, implicating senescence in chronic diseases such as diabetes, obesity and atherosclerosis. Senolytics, drugs that eliminate senescent cells, afford new therapeutic strategies for control of these chronic diseases.

Endothelial sprouting, proliferation, or senescence: tipping the balance from physiology to pathology

Therapeutic modulation of vascular cell proliferation and migration is essential for the effective inhibition of angiogenesis in cancer or its induction in cardiovascular disease. The general view is that an increase in vascular growth factor levels or mitogenic stimulation is beneficial for angiogenesis, since it leads to an increase in both endothelial proliferation and sprouting. However, several recent studies showed that an increase in mitogenic stimuli can also lead to the arrest of angiogenesis. This is due to the existence of intrinsic signaling feedback loops and cell cycle checkpoints that work in synchrony to maintain a balance between endothelial proliferation and sprouting. This balance is tightly and effectively regulated during tissue growth and is often deregulated or impaired in disease. Most therapeutic strategies used so far to promote vascular growth simply increase mitogenic stimuli, without taking into account its deleterious effects on this balance and on vascular cells. Here, we review the main findings on the mechanisms controlling physiological vascular sprouting, proliferation, and senescence and how those mechanisms are often deregulated in acquired or congenital cardiovascular disease leading to a diverse range of pathologies. We also discuss alternative approaches to increase the effectiveness of pro-angiogenic therapies in cardiovascular regenerative medicine.

Designing Biomaterials to Modulate Notch Signaling in Tissue Engineering and Regenerative Medicine

The design of cell-instructive biomaterials for tissue engineering and regenerative medicine is at a crossroads. Although the conventional tissue engineering approach is top-down (cells seeded to macroporous scaffolds and mature to form tissues), bottom-up tissue engineering strategies are becoming appealing. With such developments, we can study cell signaling events, thus enabling functional tissue assembly in physiologic and diseased models. Among many important signaling pathways, the Notch signaling pathway is the most diverse in its influence during tissue morphogenesis and repair following injury. Although Notch signaling is extensively studied in developmental biology and cancer biology, our knowledge of designing biomaterial-based Notch signaling platforms and incorporating Notch signaling components into engineered tissue systems is limited. By incorporating Notch signaling to tissue engineering scaffolds, we can direct cell-specific responses and improve engineered tissue maturation. This review will discuss recent progress in the development of Notch signaling biomaterials as a promising target to control cellular fate decisions, including the influences of ligand identity, biophysical material cues, ligand presentation strategies, and mechanotransduction. Notch signaling is consequently of interest to direct, control, and reprogram cellular behavior on a biomaterial surface. We anticipate that discussions in this article will allow for enhanced knowledge and insight into designing Notch targeted biomaterials for various tissue engineering and cell fate determinations. Impact statement Notch signaling is recognized as an important pathway in tissue engineering and regenerative medicine; however, there is no systematic review on this topic. The comprehensive review and perspectives presented here provide an in-depth discussion on ligand presentation strategies both in 2D and in 3D cell culture environments involving biomaterials/scaffolds. In addition, this review article provides insight into the challenges in designing cell surrogate biomaterials capable of providing Notch signals. To the best of the authors' knowledge, this is the first review relevant to the fields of tissue engineering.

Inhibition of notch enhances the anti-atherosclerotic effects of LXR agonists while reducing fatty liver development in ApoE-deficient mice

Liver X receptor (LXR) activation can achieve satisfactory anti-atherosclerotic activity, but can also lead to the development of fatty liver and hypertriglyceridemia. In contrast, Notch inhibition can suppress both atherosclerosis and the hepatic accumulation of lipids. In the present study, we sought to assess whether combining LXR ligand agonists (T317) with Notch receptor inhibitors (DAPT) would lead to enhanced anti-atherosclerotic activity while overcoming the adverse events associated with LXR ligand agonist therapy. The impact of the combined T317 + DAPT therapeutic regimen on atherosclerosis, fatty liver development, and hypertriglyceridemia was assessed using ApoE deficient (ApoE^-/-) mice. The results of this analysis suggested that DAPT was able to improve the anti-atherosclerotic activity of T317 without reducing the stability of lesion plaques while simultaneously reducing blood lipids in treated ApoE^-/- mice. This combination T317 + DAPT treatment was also linked with a significant upregulation of ABCA1 and the stimulation of reverse cholesterol transport (RCT), as well as with decreases in the levels of intercellular cell adhesion molecule-1 (ICAM-1) and p-p65, and with altered M1/M2 macrophage proportions within atherosclerotic plaques. Importantly, DAPT was also able to reduce T317-mediated lipid accumulation within the liver owing to its ability to reduce SREBP-1 expression while simultaneously increasing that of Pi-AMPKα and PPARα. Together, our results suggest that administering Notch receptor inhibitors to ApoE^-/- mice may be an effective means of enhancing the anti-atherosclerotic activity of LXR ligand agonists while simultaneously limiting associated fatty liver and hypertriglyceridemia development in these animals.

Chronic Nucleoside Reverse Transcriptase Inhibitors Disrupt Mitochondrial Homeostasis and Promote Premature Endothelial Senescence

Combination antiretroviral therapy (cART) has improved the life expectancy of HIV patients, thus increasing the number of people living with HIV (PLWH). However, cardiovascular diseases (CVD) are now one of the most prevalent causes of death among PLWH. Nucleoside reverse transcriptase inhibitors (NRTIs) are the backbone of cART, and the emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) coformulation is commonly used. In prior studies, acute NRTI treatment-induced endothelial dysfunction, increased reactive oxygen species production, and mitophagic activity, suggesting that mitochondrial dysfunction may be critical to NRTI-induced endothelial dysfunction. Mitochondrial dysfunction plays a causal role in endothelial senescence, whereas premature endothelial senescence can promote the development of CVD. We hypothesize that for chronic NRTI treatment, a disruption in mitochondrial homeostasis leads to premature endothelial senescence and predisposes PLWH to CVD. We used human aortic endothelial cells (HAEC) and HIV-1 transgenic (Tg26) mice to test the interrelationship between mitochondrial and vascular dysfunction after chronic NRTI treatment in vitro and in vivo. Mitochondrial DNA copy number was decreased in late-passage HAEC treated with NRTIs, and senescence-associated β-galactosidase accumulation was elevated. In late-passage HAEC, NRTIs decreased the activity of Parkin-mediated mitophagy. In Tg26 mice treated with FTC, plasma nitrite levels were decreased. Endothelium-dependent vasodilation in NRTI-treated Tg26 mice was also reduced. Our work suggests that long-term use of NRTI may disrupt mitochondrial homeostasis, induce premature endothelial senescence, and impair vascular function.

Effect of Active Ingredients of Chinese Herbal Medicine on the Rejuvenation of Healthy Aging: Focus on Stem Cells

Stem cells (SCs) are special types of cells with the ability of self-renewal and multidirectional differentiation. As the organism ages, the ability to maintain homeostasis and regeneration deteriorates and the number and activity of stem cells decline. Theoretically, the restoration of stem cells might reverse aging. However, due to their own aging, donor-derived immune rejection, and difficulties in stem cell differentiation control, a series of problems need to be solved to realize the potential for clinical application of stem cells. Chinese herbal medicine is a nature drug library which is suitable for the long-term treatment of aging-related diseases. Modern pharmacological studies have revealed that many active ingredients of Chinese herbal medicines with the effect of promoting stem cells growth and differentiation mainly belong to “reinforcing herbs.” In recent years, exploration of natural active ingredients from Chinese herbal medicines for delaying aging, improving the stem cell microenvironment, and promoting the proliferation and differentiation of endogenous stem cells has attracted substantial attention. This article will focus on active ingredients from Chinese herbs-mediated differentiation of stem cells into particular cell type, like neural cells, endothelial cells, cardiomyocytes, and osteoblasts. We will also discuss the effects of these small molecules on Wnt, Sonic Hedgehog, Notch, eNOS-cGMP, and MAP kinase signal transduction pathways, as well as reveal the role of estrogen receptor α and PPAR γ on selectively promoting or inhibiting stem cells differentiation. This review will provide new insights into the health aging strategies of active ingredients in Chinese herbal medicine in regenerative medicine.

Vitamin C alleviates the senescence of periodontal ligament stem cells through inhibition of Notch3 during long-term culture

Periodontal ligament stem cells (PDLSCs), as potential "seed cells" for periodontal tissue repair and regeneration, require to be expanded in vitro for a large scale. Senescence of PDLSCs occurred during long-term culture may compromise the therapeutic effects of PDLSCs. Medium supplements may be useful in antisenescence. However, the effects and mechanisms of vitamin C (Vc) treatment on PDLSCs during long-term culture are still unclear. In this study, we identified that Vc-treated PDLSCs cells maintained a slender morphology, higher growth rate and migration capacity, stemness, and osteogenic differentiation capability during a long-term culture. Moreover, we also identified that Notch3 was significantly upregulated during the cell senescence, and Vc treatment alleviated the senescence of PDLSCs through inhibition of Notch3 during long-term culture. In summary, Vc treatment suppressed PDLSCs senescence by reducing the expression of Notch3 and might be a simple and useful strategy to inhibit cellular senescence during the cell long-term culture.

Rosiglitazone ameliorates senescence and promotes apoptosis in ovarian cancer induced by olaparib

OBJECTIVE

Senescence mechanisms are vital to resistance to long-term olaparib maintenance treatment. Recently, peroxisome proliferator-activated receptor-γ agonists (e.g., rosiglitazone) have been reported to ameliorate the senescence-like phenotype by modulating inflammatory mediator production. This study examined synergistic effects on the anti-tumor activity of rosiglitazone combined with olaparib in ovarian cancer treatment.

METHODS

A2780 and SKOV3 mouse subcutaneous xenograft models were established for observing anti-tumor effects in living organisms and were randomly split into combination (both olaparib and rosiglitazone), rosiglitazone (10 mg/kg), olaparib (10 mg/kg), control (solvent) groups that received treatment once every 2 or 3 days (n = 6 per group). Cell counting kit-8 (CCK-8) assays were used to test the influences of rosiglitazone and olaparib on cell proliferation. PI and Annexin-V-FITC staining was used with flow cytometry to assess the cell cycle distribution and cell apoptosis. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to observe cellular senescence. We performed quantitative real-time polymerase chain reaction assays to study the senescence-related secretory phenotype (SASP).

RESULTS

Olaparib and rosiglitazone were observed to synergistically retard subcutaneous ovarian cancer growth in vivo, and synergistically suppress ovarian cancer cell proliferation in vitro. Compared with olaparib alone, the percentage of positive cells expressed SA-β-gal and SASP were significantly decreased in the treatment of combination of olaparib and rosiglitazone. Furthermore, olaparib plus rosiglitazone increased the percentage of apoptosis in ovarian cancer cell compared with olaparib alone. In A2780 cells, it showed lower expression of P53, phospho-p53 (Ser15), P21, and P18 protein in combination treatment compared with olaparib alone. While, in SKOV3 cells, it showed lower expression of phosphor-retinoblastoma protein (Rb) (Ser807/811), and higher expression of cyclin D1, P21, and P16 protein in combination treatment compared with olaparib alone.

CONCLUSIONS

Rosiglitazone combined with olaparib can help manage ovarian cancer by ameliorating olaparib-induced senescence and improving anti-tumor effects.

Regulation of calcium pump through Notch/Jagged/Hes signaling pathway in canine model of chronic atrial fibrillation

OBJECTIVE

Using a canine model of atrial fibrillation (AF) induced by chronic pacing of left atrial fibrillation, the present study aimed to investigate the protein expression and content change of Notch-1 and its downstream target genes including Hes1, Jagged1, and SERCA2a in the atrial myocardium of canines with chronic AF. Furthermore, the correlation between Notch-1/Hes1/Jagged1 and the SERCA2a calcium pump was also analyzed.

METHODS

Ten healthy Beagle dogs including both males and females, aged 7-9 years were randomly divided into a sham group (n = 5) and AF group (n = 5). The AF group underwent minimally invasive surgery with implantation of a pacemaker into the left atrial appendage for induction of AF. After 8 weeks of pacemaker implantation, animals were euthanized and specimens from the right and left atrial free walls were excised for histologic and biochemical analyses.

RESULTS

After 8 weeks' pacemaker implantation, immunohistochemical expression of Notch-1, Hes1, Jagget1 and SERCA2a in the sham group was positive. Compared with the sham operation group, the intensity of Notch-1, Hes1 and Jagget1 in AF group was stronger with a significant increasing trend in the intensity of the color, respectively. The expression of SERCA2a was weak; the intensity decreased significantly (P < 0.05). Pearson correlation analysis revealed that in the AF group, Notch-1 was negatively correlated with SERCA2a (r = -0.77, P = 0.028), and was positively correlated with Hes1 and Jagged1 (r = 0.92, P = 0.014; r = 0.73, P = 0.030) proteins, respectively.

CONCLUSION

The activation of the Notch signaling pathway was associated with a decrease in SERCA2a protein expression and contributes to the development and maintenance of electrical remodeling in AF through modulation of calcium pump function and calcium homeostasis.

Pyrroloquinoline quinone delays inflammaging induced by TNF-α through the p16/p21 and Jagged1 signalling pathways

Previous studies on the longevity effect of pyrroloquinoline quinine (PQQ) on nematode worms have revealed that PQQ can enhance the antioxidant capacity of nematode worms, thus extending the lifespan of the worms. The induction and development of cellular senescence are closely connected with inflammatory reactions. The aim of this study was to determine the effect of PQQ and ageing factors on senescent cells. To this end, we cultivated human embryonic lung fibroblasts in nutrient solution with or without tumour necrosis factor-alpha (TNF-α) to establish an inflammaging model in vitro. The cells were preincubated with or without PQQ to determine if PQQ had any anti-inflammaging effect. More senescent cells were detected with the addition of TNF-α than without (P < .01). The ratio of senescent cells to non-senescent cells in the TNF-α group was greater than that in the control group (P < .01). When cells were preincubated with PQQ prior to TNF-α treatment, there were fewer senescent cells than those in the control group, which was not pretreated with PQQ (P < .05). The same tendency was noted with regard to p21, p16, and Jagged1. In summary, we used TNF-α, a well-known pro-inflammatory cytokine associated with inflammaging, to establish an in vitro inflammaging model and provided evidence that PQQ delays TNF-α -induced cellular senescence and has anti-inflammaging properties.

miR-133b Downregulation Reduces Vulnerable Plaque Formation in Mice with AS through Inhibiting Macrophage Immune Responses

Atherosclerosis (AS) is a chronic inflammatory disease characterized by accumulating deposition of lipids in the arterial intima. Notably, macrophages participate centrally in the pathogenesis of this deadly disease. In this study, we established AS mouse models in order to investigate the effect of microRNA-133b (miR-133b) on vulnerable plaque formation and vascular remodeling in AS and explore the potential functional mechanisms. The expression of miR-133b was altered or the Notch-signaling pathway was blocked in the AS mouse models in order to evaluate the proliferation, migration, and apoptosis of macrophages. It was observed that miR-133b was upregulated in AS, which might target MAML1 to regulate the Notch-signaling pathway. AS mice with downregulated miR-133b or inhibited Notch-signaling pathway presented with a reduced AS plaque area, a decreased positive rate of macrophages, and an increased positive rate of vascular smooth muscle cells. Moreover, Notch-signaling pathway blockade or miR-133b downregulation inhibited the macrophage viability and migration and accelerated the apoptosis. This study provides evidence that downregulated miR-133b expression may inhibit the immune responses of macrophages and attenuate the vulnerable plaque formation and vascular remodeling in AS mice through the MAML1-mediated Notch-signaling pathway, highlighting miR-133b as a novel therapeutic target for AS.

The Use of Nutraceuticals to Counteract Atherosclerosis: The Role of the Notch Pathway

Despite the currently available pharmacotherapies, today, thirty percent of worldwide deaths are due to cardiovascular diseases (CVDs), whose primary cause is atherosclerosis, an inflammatory disorder characterized by the buildup of lipid deposits on the inside of arteries. Multiple cellular signaling pathways have been shown to be involved in the processes underlying atherosclerosis, and evidence has been accumulating for the crucial role of Notch receptors in regulating the functions of the diverse cell types involved in atherosclerosis onset and progression. Several classes of nutraceuticals have potential benefits for the prevention and treatment of atherosclerosis and CVDs, some of which could in part be due to their ability to modulate the Notch pathway. In this review, we summarize the current state of knowledge on the role of Notch in vascular health and its modulation by nutraceuticals for the prevention of atherosclerosis and/or treatment of related CVDs.

NOTCH1 signaling induces pathological vascular permeability in diabetic retinopathy

Diabetic macular edema is a major complication of diabetes resulting in loss of central vision. Although heightened vessel leakiness has been linked to glial and neuronal-derived factors, relatively little is known on the mechanisms by which mature endothelial cells exit from a quiescent state and compromise barrier function. Here we report that endothelial NOTCH1 signaling in mature diabetic retinas contributes to increased vascular permeability. By providing both human and mouse data, we show that NOTCH1 ligands JAGGED1 and DELTA LIKE-4 are up-regulated secondary to hyperglycemia and activate both canonical and rapid noncanonical NOTCH1 pathways that ultimately disrupt endothelial adherens junctions in diabetic retinas by causing dissociation of vascular endothelial-cadherin from β-catenin. We further demonstrate that neutralization of NOTCH1 ligands prevents diabetes-induced retinal edema. Collectively, these results identify a fundamental process in diabetes-mediated vascular permeability and provide translational rational for targeting the NOTCH pathway (primarily JAGGED1) in conditions characterized by compromised vascular barrier function.

A comparison of resveratrol and other polyphenolic compounds on Notch activation and endothelial cell activity

Resveratrol is a polyphenolic compound produced by plants which makes its way into the human diet through plant-based foods. It has been shown to provide many health benefits, helping to ward of age-related diseases and promoting cardiovascular health. Additionally, resveratrol is a potent activator of the Notch signaling pathway. While resveratrol receives the most attention as a polyphenolic nutraceutical, other compounds with similar structures may be more potent regulators of specific cellular processes. Here, we compare resveratrol, apigenin, chrysin, genistein, luteolin, myricetin, piceatannol, pterostilbene, and quercetin for their ability to regulate Notch signaling. In addition, we compare the ability of these polyphenolic compounds to regulate endothelial cell viability, proliferation, and migration. Out of these compounds we found that resveratrol is the best activator of Notch signaling, however, other similar compounds are also capable of stimulating Notch. We also discovered that several of these polyphenols were able to inhibit endothelial cell proliferation. Finally, we found that many of these polyphenols are potent inhibitors of endothelial migration during wound healing assays. These findings provide the first side-by-side comparison of the regulation of Notch signaling, and endothelial cell proliferation and migration, by nine polyphenolic compounds.

A prospect of cell immortalization combined with matrix microenvironmental optimization strategy for tissue engineering and regeneration

Cellular senescence is a major hurdle for primary cell-based tissue engineering and regenerative medicine. Telomere erosion, oxidative stress, the expression of oncogenes and the loss of tumor suppressor genes all may account for the cellular senescence process with the involvement of various signaling pathways. To establish immortalized cell lines for research and clinical use, strategies have been applied including internal genomic or external matrix microenvironment modification. Considering the potential risks of malignant transformation and tumorigenesis of genetic manipulation, environmental modification methods, especially the decellularized cell-deposited extracellular matrix (dECM)-based preconditioning strategy, appear to be promising for tissue engineering-aimed cell immortalization. Due to few review articles focusing on this topic, this review provides a summary of cell senescence and immortalization and discusses advantages and limitations of tissue engineering and regeneration with the use of immortalized cells as well as a potential rejuvenation strategy through combination with the dECM approach.

NOTCH regulation of the endothelial cell phenotype

Purpose of review

The formation of a hierarchical vascular network is a complex process that requires precise temporal and spatial integration of several signaling pathways. Amongst those, Notch has emerged as a key regulator of multiple steps that expand from endothelial sprouting to arterial specification and remains relevant in the adult. This review aims to summarize major concepts and rising hypotheses on the role of Notch signaling in the endothelium.

Recent findings

A wealth of new information has helped to clarify how Notch signaling cooperates with other pathways to orchestrate vascular morphogenesis, branching, and function. Endothelial vascular endothelial growth factor, C-X-C chemokine receptor type 4, and nicotinamide adenine dinucleotide phosphate oxidase 2 have been highlighted as key regulators of the pathway. Furthermore, blood flow forces during vascular development induce Notch1 signaling to suppress endothelial cell proliferation, enhance barrier function, and promote arterial specification. Importantly, Notch1 has been recently recognized as an endothelial mechanosensor that is highly responsive to the level of shear stress to enable differential Notch activation in distinct regions of the vessel wall and suppress inflammation.

Summary

Although it is well accepted that the Notch signaling pathway is essential for vascular morphogenesis, its contributions to the homeostasis of adult endothelium were uncovered only recently. Furthermore, its exquisite regulation by flow and impressive interface with multiple signaling pathways indicates that Notch is at the center of a highly interactive web that integrates both physical and chemical signals to ensure vascular stability.

Effects of diosgenin and its derivatives on atherosclerosis

The effects of diosgenin are discussed with respect to endothelial dysfunction, lipid profile, macrophage foam cell formation, VSMC viability, thrombosis and inflammation during the formation of atherosclerosis.

Proteomic analysis of heart failure hospitalization among patients with chronic kidney disease: The Heart and Soul Study

Background

Patients with chronic kidney disease (CKD) are at increased risk for heart failure (HF). We aimed to investigate differences in proteins associated with HF hospitalizations among patients with and without CKD in the Heart and Soul Study.

Methods and results

We measured 1068 unique plasma proteins from baseline samples of 974 participants in The Heart and Soul Study who were followed for HF hospitalization over a median of 7 years. We sequentially applied forest regression and Cox survival analyses to select prognostic proteins. Among participants with CKD, four proteins were associated with HF at Bonferroni-level significance (p<2.5x10^-4): Angiopoietin-2 (HR[95%CI] 1.45[1.33, 1.59]), Spondin-1 (HR[95%CI] 1.13 [1.06, 1.20]), tartrate-resistant acid phosphatase type 5 (HR[95%CI] 0.65[0.53, 0.78]) and neurogenis locus notch homolog protein 1 (NOTCH1) (HR[95%CI] 0.67[0.55, 0.80]). These associations persisted at p<0.01 after adjustment for age, estimated glomerular filtration and history of HF. CKD was a significant interaction term in the associations of NOTCH1 and Spondin-1 with HF. Pathway analysis showed a trend for higher representation of the Cardiac Hypertrophy and Complement/Coagulation pathways among proteins prognostic of HF in the CKD sub-group.

Conclusions

These results suggest that markers of heart failure differ between patients with and without CKD. Further research is needed to validate novel markers in cohorts of patients with CKD and adjudicated HF events.

Molecular interaction of NFκB and NICD in monocyte-macrophage differentiation is a target for intervention in atherosclerosis

The activation of two transcription factors, NFκB and NICD (notch intracellular domain), plays a crucial role in different stages of atherosclerotic disease progression, from early endothelial activation by modified lipids like oxidized low-density lipoprotein (oxyLDL) to the imminent rupture of the atherosclerotic plaque. Inflammatory mediators and the notch pathway proteins were upregulated in atherogenic diet-induced rats and the same was confirmed by the differentiation of monocyte to macrophage on exposure to oxyLDL. The inflammatory transcription factor NFκB and the notch signaling transcription factor NICD were analysed for their molecular interaction in monocyte to macrophage differentiation. Inhibition of NFκB by dexamethasone in monocyte to macrophage differentiation resulted in a concomitant downregulation of NICD, whereas inhibition of NICD by N-(N-[3, 5-difluorophenacetyl])-l-alanyl)-S-phenylglycine t-butyl ester (DAPT), a γ-secretase inhibitor, did not significantly influence the expression of NFκB, but downregulated macrophage differentiation. These findings revealed that NFκB inhibition using dexamethasone regulated NICD, which turned down macrophage differentiation. Thus, inhibition of both NFκB-NICD is a potential target for intervention in atherosclerosis.

Metabolic Regulation of Angiogenesis in Diabetes and Aging

Impaired angiogenesis and endothelial dysfunction are hallmarks of diabetes and aging. Clinical efforts at promoting angiogenesis have largely focused on growth factor pathways, with mixed results. Recently, a new repertoire of endothelial intracellular molecules critical to endothelial metabolism has emerged as playing an important role in regulating angiogenesis. This review thus focuses on the emerging importance and therapeutic potential of these proteins and of endothelial bioenergetics in diabetes and aging.

Notch Signaling as a Regulator of the Tumor Immune Response: To Target or Not To Target?

The Notch signaling pathway regulates important cellular processes involved in stem cell maintenance, proliferation, development, survival, and inflammation. These responses to Notch signaling involving both canonical and non-canonical pathways can be spatially and temporally variable and are highly cell-type dependent. Notch signaling can elicit opposite effects in regulating tumorigenicity (tumor-promoting versus tumor-suppressing function) as well as controlling immune cell responses. In various cancer types, Notch signaling elicits a "cancer stem cell (CSC)" phenotype that results in decreased proliferation, but resistance to various therapies, hence potentially contributing to cell dormancy and relapse. CSCs can reshape their niche by releasing paracrine factors and inflammatory cytokines, and the niche in return can support their quiescence and resistance to therapies as well as the immune response. Moreover, Notch signaling is one of the key regulators of hematopoiesis, immune cell differentiation, and inflammation and is implicated in various autoimmune diseases, carcinogenesis (leukemia), and tumor-induced immunosuppression. Notch can control the fate of various T cell types, including Th1, Th2, and the regulatory T cells (Tregs), and myeloid cells including macrophages, dendritic cells, and myeloid-derived suppressor cells (MDSCs). Both MDSCs and Tregs play an important role in supporting tumor cells (and CSCs) and in evading the immune response. In this review, we will discuss how Notch signaling regulates multiple aspects of the tumor-promoting environment by elucidating its role in CSCs, hematopoiesis, normal immune cell differentiation, and subsequently in tumor-supporting immunogenicity.

Shear stress, arterial identity and atherosclerosis

In the developing embryo, the vasculature first takes the form of a web-like network called the vascular plexus. Arterial and venous differentiation is subsequently guided by the specific expression of genes in the endothelial cells that provide spatial and temporal cues for development. Notch1/4, Notch ligand delta-like 4 (Dll4), and Notch downstream effectors are typically expressed in arterial cells along with EphrinB2, whereas chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and EphB4 characterise vein endothelial cells. Haemodynamic forces (blood pressure and blood flow) also contribute importantly to vascular remodelling. Early arteriovenous differentiation and local blood flow may hold the key to future inflammatory diseases. Indeed, despite the fact that atherosclerosis risk factors such as smoking, hypertension, hypercholesterolaemia, and diabetes all induce endothelial cell dysfunction throughout the vasculature, plaques develop only in arteries, and they localise essentially in vessel branch points, curvatures and bifurcations, where blood flow (and consequently shear stress) is low or oscillatory. Arterial segments exposed to high blood flow (and high laminar shear stress) tend to remain plaque-free. These observations have led many to investigate what particular properties of arterial or venous endothelial cells confer susceptibility or protection from plaque formation, and how that might interact with a particular shear stress environment.