Cell senescence: basic mechanisms and the need for computational networks in vascular ageing

N6-Methyladenosine in Vascular Aging and Related Diseases: Clinical Perspectives

Aging leads to progressive deterioration of the structure and function of arteries, which eventually contributes to the development of vascular aging-related diseases. N6-methyladenosine (m6A) is the most prevalent modification in eukaryotic RNAs. This reversible m6A RNA modification is dynamically regulated by writers, erasers, and readers, playing a critical role in various physiological and pathological conditions by affecting almost all stages of the RNA life cycle. Recent studies have highlighted the involvement of m6A in vascular aging and related diseases, shedding light on its potential clinical significance. In this paper, we comprehensively discuss the current understanding of m6A in vascular aging and its clinical implications. We discuss the molecular insights into m6A and its association with clinical realities, emphasizing its significance in unraveling the mechanisms underlying vascular aging. Furthermore, we explore the possibility of m6A and its regulators as clinical indicators for early diagnosis and prognosis prediction and investigate the therapeutic potential of m6A-associated anti-aging approaches. We also examine the challenges and future directions in this field and highlight the necessity of integrating m6A knowledge into patient-centered care. Finally, we emphasize the need for multidisciplinary collaboration to advance the field of m6A research and its clinical application.

Immune and inflammatory mechanisms in hypertension

Hypertension is a global health problem, with >1.3 billion individuals with high blood pressure worldwide. In this Review, we present an inflammatory paradigm for hypertension, emphasizing the crucial roles of immune cells, cytokines and chemokines in disease initiation and progression. T cells, monocytes, macrophages, dendritic cells, B cells and natural killer cells are all implicated in hypertension. Neoantigens, the NLRP3 inflammasome and increased sympathetic outflow, as well as cytokines (including IL-6, IL-7, IL-15, IL-18 and IL-21) and a high-salt environment, can contribute to immune activation in hypertension. The activated immune cells migrate to target organs such as arteries (especially the perivascular fat and adventitia), kidneys, the heart and the brain, where they release effector cytokines that elevate blood pressure and cause vascular remodelling, renal damage, cardiac hypertrophy, cognitive impairment and dementia. IL-17 secreted by CD4+ T helper 17 cells and γδ T cells, and interferon-γ and tumour necrosis factor secreted by immunosenescent CD8+ T cells, exert crucial effector roles in hypertension, whereas IL-10 and regulatory T cells are protective. Effector mediators impair nitric oxide bioavailability, leading to endothelial dysfunction and increased vascular contractility. Inflammatory effector mediators also alter renal sodium and water balance and promote renal fibrosis. These mechanisms link hypertension with obesity, autoimmunity, periodontitis and COVID-19. A comprehensive understanding of the immune and inflammatory mechanisms of hypertension is crucial for safely and effectively translating the findings to clinical practice.

Arterial Stiffness: From Basic Primers to Integrative Physiology

The elastic properties of conductance arteries are one of the most important hemodynamic functions in the body, and data continue to emerge regarding the importance of their dysfunction in vascular aging and a range of cardiovascular diseases. Here, we provide new insight into the integrative physiology of arterial stiffening and its clinical consequence. We also comprehensively review progress made on pathways/molecules that appear today as important basic determinants of arterial stiffness, particularly those mediating the vascular smooth muscle cell (VSMC) contractility, plasticity and stiffness. We focus on membrane and nuclear mechanotransduction, clearance function of the vascular wall, phenotypic switching of VSMCs, immunoinflammatory stimuli and epigenetic mechanisms. Finally, we discuss the most important advances of the latest clinical studies that revisit the classical therapeutic concepts of arterial stiffness and lead to a patient-by-patient strategy according to cardiovascular risk exposure and underlying disease.

Cyclin-Dependent Kinase Inhibitor 2A is a Key Regulator of Cell Cycle Arrest and Senescence in Endothelial Colony-Forming Cells in Moyamoya Disease

OBJECTIVE

Endothelial colony-forming cells (ECFCs) have been reported to play an important role in the pathogenesis of moyamoya disease (MMD). We have previously observed stagnant growth in MMD ECFCs with functional impairment of tubule formation. We aimed to verify the key regulators and related signaling pathways involved in the functional defects of MMD ECFCs.

METHODS

ECFCs were cultured from peripheral blood mononuclear cells of healthy volunteers (normal) and MMD patients. Low-density lipoproteins uptake, flow cytometry, high content screening, senescence-associated β-galactosidase, immunofluorescence, cell cycle, tubule formation, microarray, real-time quantitative polymerase chain reaction, small interfering RNA transfection, and western blot analyses were performed.

RESULTS

The acquisition of cells that can be cultured for a long time with the characteristics of late ECFCs was significantly lower in the MMD patients than the normal. Importantly, the MMD ECFCs showed decreased cellular proliferation with G1 cell cycle arrest and cellular senescence compared to the normal ECFCs. A pathway enrichment analysis demonstrated that the cell cycle pathway was the major enriched pathway, which is consistent with the results of the functional analysis of ECFCs. Among the genes associated with the cell cycle, cyclin-dependent kinase inhibitor 2A (CDKN2A) showed the highest expression in MMD ECFCs. Knockdown of CDKN2A in MMD ECFCs enhanced proliferation by reducing G1 cell cycle arrest and inhibiting senescence through the regulation of CDK4 and phospho retinoblastoma protein.

CONCLUSION

Our study suggests that CDKN2A plays an important role in the growth retardation of MMD ECFCs by inducing cell cycle arrest and senescence.

Disrupted Binding of Cystathionine γ-Lyase to p53 Promotes Endothelial Senescence

BACKGROUND

Advanced age is unequivocally linked to the development of cardiovascular disease; however, the mechanisms resulting in reduced endothelial cell regeneration remain poorly understood. Here, we investigated novel mechanisms involved in endothelial cell senescence that impact endothelial cell transcription and vascular repair after injury.

METHODS

Native endothelial cells were isolated from young (20±3.4 years) and aged (80±2.3 years) individuals and subjected to molecular analyses to assess global transcriptional and metabolic changes. In vitro studies were conducted using primary human and murine endothelial cells. A murine aortic re-endothelialization model was used to examine endothelial cell regenerative capacity in vivo.

RESULTS

RNA sequencing of native endothelial cells revealed that aging resulted in p53-mediated reprogramming to express senescence-associated genes and suppress glycolysis. Reduced glucose uptake and ATP contributed to attenuated assembly of the telomerase complex, which was required for endothelial cell proliferation. Enhanced p53 activity in aging was linked to its acetylation on K120 due to enhanced activity of the acetyltransferase MOZ (monocytic leukemic zinc finger). Mechanistically, p53 acetylation and translocation were, at least partially, attributed to the loss of the vasoprotective enzyme, CSE (cystathionine γ-lyase). CSE physically anchored p53 in the cytosol to prevent its nuclear translocation and CSE absence inhibited AKT (Protein kinase B)-mediated MOZ phosphorylation, which in turn increased MOZ activity and subsequently p53 acetylation. In mice, the endothelial cell-specific deletion of CSE activated p53, induced premature endothelial senescence, and arrested vascular repair after injury. In contrast, the adeno-associated virus 9-mediated re-expression of an active CSE mutant retained p53 in the cytosol, maintained endothelial glucose metabolism and proliferation, and prevented endothelial cell senescence. Adenoviral overexpression of CSE in native endothelial cells from aged individuals maintained low p53 activity and reactivated telomerase to revert endothelial cell senescence.

CONCLUSIONS

Aging-associated impairment of vascular repair is partly determined by the vasoprotective enzyme CSE.

Therapeutic potential of nitric oxide in vascular aging due to the promotion of angiogenesis

The decrease in angiogenesis that occurs with aging significantly contributes to the higher incidence and mortality of cardiovascular diseases among the elderly. This decline in angiogenesis becomes more pronounced with increasing age and is closely linked to abnormal function and senescence of endothelial cells. Enhancing angiogenesis in aging and targeting senescent endothelial cells have gained considerable attention. Nitric oxide (NO) has been thoroughly investigated for its function in regulating angiogenesis and is an important factor that can counteract endothelial cell senescence. This review summarizes the mechanisms of reduced angiogenesis during aging and therapeutic strategies targeting senescent cells. We also discuss the potential of combining the current approaches with NO in promoting angiogenesis in aging vessels.

Endothelial mechanobiology in atherosclerosis

Cardiovascular disease (CVD) is a serious health challenge, causing more deaths worldwide than cancer. The vascular endothelium, which forms the inner lining of blood vessels, plays a central role in maintaining vascular integrity and homeostasis and is in direct contact with the blood flow. Research over the past century has shown that mechanical perturbations of the vascular wall contribute to the formation and progression of atherosclerosis. While the straight part of the artery is exposed to sustained laminar flow and physiological high shear stress, flow near branch points or in curved vessels can exhibit 'disturbed' flow. Clinical studies as well as carefully controlled in vitro analyses have confirmed that these regions of disturbed flow, which can include low shear stress, recirculation, oscillation, or lateral flow, are preferential sites of atherosclerotic lesion formation. Because of their critical role in blood flow homeostasis, vascular endothelial cells (ECs) have mechanosensory mechanisms that allow them to react rapidly to changes in mechanical forces, and to execute context-specific adaptive responses to modulate EC functions. This review summarizes the current understanding of endothelial mechanobiology, which can guide the identification of new therapeutic targets to slow or reverse the progression of atherosclerosis.

Conductance Artery Wall Layers and Their Respective Roles in the Clearance Functions

Evolutionary organization of the arterial wall into layers occurred concomitantly with the emergence of a highly muscularized, pressurized arterial system that facilitates outward hydraulic conductance and mass transport of soluble substances across the arterial wall. Although colliding circulating cells disperse potential energy within the arterial wall, the different layers counteract this effect: (1) the endothelium ensures a partial barrier function; (2) the media comprises smooth muscle cells capable of endocytosis/phagocytosis; (3) the outer adventitia and perivascular adipocytic tissue are the final receptacles of convected substances. While the endothelium forms a physical and a biochemical barrier, the medial layer is avascular, relying on the specific permeability properties of the endothelium for metabolic support. Different components of the media interact with convected molecules: medial smooth muscle cells take up numerous molecules via scavenger receptors and are capable of phagocytosis of macro/micro particles. The outer layers-the highly microvascularized innervated adventitia and perivascular adipose tissue-are also involved in the clearance functions of the media: the adventitia is the seat of immune response development, inward angiogenesis, macromolecular lymphatic drainage, and neuronal stimulation. Consequently, the clearance functions of the arterial wall are physiologically essential, but also may favor the development of arterial wall pathologies. This review describes how the walls of large conductance arteries have acquired physiological clearance functions, how this is determined by the attributes of the endothelial barrier, governed by endocytic and phagocytic capacities of smooth muscle cells, impacting adventitial functions, and the role of these clearance functions in arterial wall diseases.

Translation of Cellular Senescence to Novel Therapeutics: Insights From Alternative Tools and Models

Increasing chronological age is the greatest risk factor for human diseases. Cellular senescence (CS), which is characterized by permanent cell-cycle arrest, has recently emerged as a fundamental mechanism in developing aging-related pathologies. During the aging process, senescent cell accumulation results in senescence-associated secretory phenotype (SASP) which plays an essential role in tissue dysfunction. Although discovered very recently, senotherapeutic drugs have been already involved in clinical studies. This review gives a summary of the molecular mechanisms of CS and its role particularly in the development of cardiovascular diseases (CVD) as the leading cause of death. In addition, it addresses alternative research tools including the nonhuman and human models as well as computational techniques for the discovery of novel therapies. Finally, senotherapeutic approaches that are mainly classified as senolytics and senomorphics are discussed.

Cellular Senescence in Cardiovascular Diseases: A Systematic Review

Aging is a prominent risk factor for cardiovascular diseases, which is the leading cause of death around the world. Recently, cellular senescence has received potential attention as a promising target in preventing cardiovascular diseases, including acute myocardial infarction, atherosclerosis, cardiac aging, pressure overload-induced hypertrophy, heart regeneration, hypertension, and abdominal aortic aneurysm. Here, we discuss the mechanisms underlying cellular senescence and describe the involvement of senescent cardiovascular cells (including cardiomyocytes, endothelial cells, vascular smooth muscle cells, fibroblasts/myofibroblasts and T cells) in age-related cardiovascular diseases. Then, we highlight the targets (SIRT1 and mTOR) that regulating cellular senescence in cardiovascular disorders. Furthermore, we review the evidence that senescent cells can exert both beneficial and detrimental implications in cardiovascular diseases on a context-dependent manner. Finally, we summarize the emerging pro-senescent or anti-senescent interventions and discuss their therapeutic potential in preventing cardiovascular diseases.

OUP accepted manuscript

Cardiovascular diseases (CVDs) arise from a complex interplay among genomic, proteomic, and metabolomic abnormalities. Emerging evidence has recently consolidated the presence of robust DNA damage in a variety of cardiovascular disorders. DNA damage triggers a series of cellular responses termed DNA damage response (DDR) including detection of DNA lesions, cell cycle arrest, DNA repair, cellular senescence, and apoptosis, in all organ systems including hearts and vasculature. Although transient DDR in response to temporary DNA damage can be beneficial for cardiovascular function, persistent activation of DDR promotes the onset and development of CVDs. Moreover, therapeutic interventions that target DNA damage and DDR have the potential to attenuate cardiovascular dysfunction and improve disease outcome. In this review, we will discuss molecular mechanisms of DNA damage and repair in the onset and development of CVDs, and explore how DDR in specific cardiac cell types contributes to CVDs. Moreover, we will highlight the latest advances regarding the potential therapeutic strategies targeting DNA damage signalling in CVDs.