Implicating endothelial cell senescence to dysfunction in the ageing and diseased brain

Regulation of blood-brain barrier integrity by Dmp1-expressing astrocytes through mitochondrial transfer

The blood-brain barrier (BBB) acts as the crucial physical filtration structure in the central nervous system. Here, we investigate the role of a specific subset of astrocytes in the regulation of BBB integrity. We showed that Dmp1-expressing astrocytes transfer mitochondria to endothelial cells via their endfeet for maintaining BBB integrity. Deletion of the Mitofusin 2 (Mfn2) gene in Dmp1-expressing astrocytes inhibited the mitochondrial transfer and caused BBB leakage. In addition, the decrease of MFN2 in astrocytes contributes to the age-associated reduction of mitochondrial transfer efficiency and thus compromises the integrity of BBB. Together, we describe a mechanism in which astrocytes regulate BBB integrity through mitochondrial transfer. Our findings provide innnovative insights into the cellular framework that underpins the progressive breakdown of BBB associated with aging and disease.

Investigating cerebral neurovascular responses to hyperglycemia in a rat model of type 2 diabetes using multimodal assessment techniques

To study neurovascular function in type 2 diabetes mellitus (T2DM), we established a high-fat diet/streptozotocin (HFD/STZ) rat model. Electrocorticography-laser speckle contrast imaging (ECoG-LSCI) revealed that the somatosensory-evoked potential (SSEP) amplitude and blood perfusion volume were significantly lower in the HFD/STZ group. Cortical spreading depression (CSD) velocity was used as a measure of neurovascular function, and the results showed that the blood flow velocity and the number of CSD events were significantly lower in the HFD/STZ group. In addition, to compare changes during acute hyperglycemia and hyperglycemia, we used intraperitoneal injection (IPI) of glucose to induce transient hyperglycemia. The results showed that CSD velocity and blood flow were significantly reduced in the IPI group. The significant neurovascular changes observed in the brains of rats in the HFD/STZ group suggest that changes in neuronal apoptosis may play a role in altered glucose homeostasis in T2DM.

Endothelial dysfunction in neurodegenerative disease: Is endothelial inflammation an overlooked druggable target?

Neurological diseases with a neurodegenerative component have been associated with alterations in the cerebrovasculature. At the anatomical level, these are centred around changes in cerebral blood flow and vessel organisation. At the molecular level, there is extensive expression of cellular adhesion molecules and increased release of pro-inflammatory mediators. Together, these has been found to negatively impact blood-brain barrier integrity. Systemic inflammation has been found to accelerate and exacerbate endothelial dysfunction, neuroinflammation and degeneration. Here, we review the role of cerebrovasculature dysfunction in neurodegenerative disease and discuss the potential contribution of intermittent pro-inflammatory systemic disease in causing endothelial pathology, highlighting a possible mechanism that may allow broad-spectrum therapeutic targeting in the future.

Alterations of the blood-brain barrier during aging

The blood-brain barrier (BBB) is a complex and dynamic interface that regulates the exchange of molecules and cells between the blood and the central nervous system. It undergoes structural and functional changes during aging, which may compromise its integrity and contribute to the pathogenesis of neurodegenerative diseases. In recent years, advances in microscopy and high-throughput bioinformatics have allowed a more in-depth investigation of the aging mechanisms of BBB. This review summarizes age-related alterations of the BBB structure and function from six perspectives: endothelial cells, astrocytes, pericytes, basement membrane, microglia and perivascular macrophages, and fibroblasts, ranging from the molecular level to the human multi-system level. These basic components are essential for the proper functioning of the BBB. Recent imaging methods of BBB were also reviewed. Elucidation of age-associated BBB changes may offer insights into BBB homeostasis and may provide effective therapeutic strategies to protect it during aging.

Long-term demyelination and aging-associated changes in mice corpus callosum; evidence for the role of accelerated aging in remyelination failure in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disorder affecting the central nervous system. Evidence suggests that age-related neurodegeneration contributes to disability progression during the chronic stages of MS. Aging is characterized by decreased regeneration potential and impaired myelin repair in the brain. It is hypothesized that accelerated cellular aging contributes to the functional decline associated with neurodegenerative diseases. We assessed the impact of aging on myelin content in the corpus callosum (CC) and compared aging with the long-term demyelination (LTD) consequents induced by 12 weeks of feeding with a cuprizone (CPZ) diet. Initially, evaluating myelin content in 2-, 6-, and 18-month-old mice revealed a reduction in myelin content, particularly at 18 months. Myelin thickness was decreased and the g-ratio increased in aged mice. Although a lower myelin content and higher g-ratio were observed in LTD model mice, compared to the normally aged mice, both aging and LTD exhibited relatively similar myelin ultrastructure. Our findings provide evidence that LTD exhibits the hallmarks of aging such as elevated expression of senescence-associated genes, mitochondrial dysfunction, and high level of oxidative stress as observed following normal aging. We also investigated the senescence-associated β-galactosidase activity in O4+ late oligodendrocyte progenitor cells (OPCs). The senescent O4+/β-galactosidase+ cells were elevated in the CPZ diet. Our data showed that the myelin degeneration in CC occurs throughout the lifespan, and LTD induced by CPZ accelerates the aging process which may explain the impairment of myelin repair in patients with progressive MS.

Unraveling the Role of the Blood-Brain Barrier in the Pathophysiology of Depression: Recent Advances and Future Perspectives

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.

Age-Related Alterations in Immune Function and Inflammation: Focus on Ischemic Stroke

The aging of the global population poses significant scientific challenges. Moreover, the biological process of aging is the most significant risk factor for most chronic illnesses; therefore, understanding the molecular and cellular mechanisms underlying these aging-related challenges is crucial for extending the healthy lifespan of older individuals. Preventing brain aging remains a priority public health goal, and integrative and comprehensive aging analyses have revealed that immunosenescence is a potential cause of age-related brain damage and disease (e.g., stroke). Importantly, the neuroinflammatory and immune systems present two-way contact and thus can affect each other. Emerging evidence supports the numerous effects of immunosenescence- and inflammation-mediated immunity in neurologically injured brains. In this study, we briefly outline how aging alters the pathophysiology and transcriptional amplitude in patients who experienced stroke and then discuss how the immune system and its cellular components and molecular mechanisms are affected by age after stroke. Finally, we highlight emerging interventions with the potential to slow down or reduce aging and prevent stroke onset.

A high-resolution view of the heterogeneous aging endothelium

Vascular endothelial cell (EC) aging has a strong impact on tissue perfusion and overall cardiovascular health. While studies confined to the investigation of aging-associated vascular readouts in one or a few tissues have already drastically expanded our understanding of EC aging, single-cell omics and other high-resolution profiling technologies have started to illuminate the intricate molecular changes underlying endothelial aging across diverse tissues and vascular beds at scale. In this review, we provide an overview of recent insights into the heterogeneous adaptations of the aging vascular endothelium. We address critical questions regarding tissue-specific and universal responses of the endothelium to the aging process, EC turnover dynamics throughout lifespan, and the differential susceptibility of ECs to acquiring aging-associated traits. In doing so, we underscore the transformative potential of single-cell approaches in advancing our comprehension of endothelial aging, essential to foster the development of future innovative therapeutic strategies for aging-associated vascular conditions.

Acute intoxication with diisopropylfluorophosphate promotes cellular senescence in the adult male rat brain

Acute intoxication with high levels of organophosphate (OP) cholinesterase inhibitors can cause cholinergic crisis, which is associated with acute, life-threatening parasympathomimetic symptoms, respiratory depression and seizures that can rapidly progress to status epilepticus (SE). Clinical and experimental data demonstrate that individuals who survive these acute neurotoxic effects often develop significant chronic morbidity, including behavioral deficits. The pathogenic mechanism(s) that link acute OP intoxication to chronic neurological deficits remain speculative. Cellular senescence has been linked to behavioral deficits associated with aging and neurodegenerative disease, but whether acute OP intoxication triggers cellular senescence in the brain has not been investigated. Here, we test this hypothesis in a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague-Dawley rats were administered DFP (4 mg/kg, s.c.). Control animals were administered an equal volume (300 µL) of sterile phosphate-buffered saline (s.c.). Both groups were subsequently injected with atropine sulfate (2 mg/kg, i.m.) and 2-pralidoxime (25 mg/kg, i.m.). DFP triggered seizure activity within minutes that rapidly progressed to SE, as determined using behavioral seizure criteria. Brains were collected from animals at 1, 3, and 6 months post-exposure for immunohistochemical analyses of p16, a biomarker of cellular senescence. While there was no immunohistochemical evidence of cellular senescence at 1-month post-exposure, at 3- and 6-months post-exposure, p16 immunoreactivity was significantly increased in the CA3 and dentate gyrus of the hippocampus, amygdala, piriform cortex and thalamus, but not the CA1 region of the hippocampus or the somatosensory cortex. Co-localization of p16 immunoreactivity with cell-specific biomarkers, specifically, NeuN, GFAP, S100β, IBA1 and CD31, revealed that p16 expression in the brain of DFP animals is neuron-specific. The spatial distribution of p16-immunopositive cells overlapped with expression of senescence associated β-galactosidase and with degenerating neurons identified by FluoroJade-C (FJC) staining. The co-occurrence of p16 and FJC was positively correlated. This study implicates cellular senescence as a novel pathogenic mechanism underlying the chronic neurological deficits observed in individuals who survive OP-induced cholinergic crisis.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

Developmental priming of early cerebrovascular ageing: Implications across a lifetime

INTRODUCTION

Neurological conditions such as Alzheimer's disease and stroke represent a substantial health burden to the world's ageing population. Cerebrovascular dysfunction is a key contributor to these conditions, affecting an individual's risk profile, age of onset, and severity of neurological disease. Recent data shows that early-life events, such as maternal health during pregnancy, birth weight and exposure to environmental toxins can 'prime' the vascular system for later changes. With age, blood vessels can become less flexible and more prone to damage. This can lead to reduced blood flow to the brain, which is associated with cognitive decline and an increased risk of stroke and other cerebrovascular diseases. These in turn increase the risk of vascular dementia and Alzheimer's disease.

OBJECTIVES

We aim to explore how early life factors influence cerebrovascular health, ageing and disease.

METHODS

We have reviewed recently published literature from epidemiological studies, clinical cases and basic research which explore mechanisms that contribute to cerebrovascular and blood-brain barrier dysfunction, with a particularly focus on those that assess contribution of early-life events or vascular priming to subsequent injury.

RESULTS

Perinatal events have been linked to acute cerebrovascular dysfunction and long-term structural reorganisation. Systemic disease throughout the lifetime that produce inflammatory or oxidative stress may further sensitise the cerebrovasculature to disease and contribute to neurodegeneration.

CONCLUSIONS

By identifying these early-life determinants and understanding their mechanisms, scientists aim to develop strategies for preventing or mitigating cerebrovascular ageing-related issues.

Proteomics of mouse brain endothelium uncovers dysregulation of vesicular transport pathways during aging

Age-related decline in brain endothelial cell (BEC) function contributes critically to neurological disease. Comprehensive atlases of the BEC transcriptome have become available, but results from proteomic profiling are lacking. To gain insights into endothelial pathways affected by aging, we developed a magnetic-activated cell sorting-based mouse BEC enrichment protocol compatible with proteomics and resolved the profiles of protein abundance changes during aging. Unsupervised cluster analysis revealed a segregation of age-related protein dynamics with biological functions, including a downregulation of vesicle-mediated transport. We found a dysregulation of key regulators of endocytosis and receptor recycling (most prominently Arf6), macropinocytosis and lysosomal degradation. In gene deletion and overexpression experiments, Arf6 affected endocytosis pathways in endothelial cells. Our approach uncovered changes not picked up by transcriptomic studies, such as accumulation of vesicle cargo and receptor ligands, including Apoe. Proteomic analysis of BECs from Apoe-deficient mice revealed a signature of accelerated aging. Our findings provide a resource for analysing BEC function during aging.

Endothelial Senescence: From Macro- to Micro-Vasculature and Its Implications on Cardiovascular Health

Endothelial cells line at the most inner layer of blood vessels. They act to control hemostasis, arterial tone/reactivity, wound healing, tissue oxygen, and nutrient supply. With age, endothelial cells become senescent, characterized by reduced regeneration capacity, inflammation, and abnormal secretory profile. Endothelial senescence represents one of the earliest features of arterial ageing and contributes to many age-related diseases. Compared to those in arteries and veins, endothelial cells of the microcirculation exhibit a greater extent of heterogeneity. Microcirculatory endothelial senescence leads to a declined capillary density, reduced angiogenic potentials, decreased blood flow, impaired barrier properties, and hypoperfusion in a tissue or organ-dependent manner. The heterogeneous phenotypes of microvascular endothelial cells in a particular vascular bed and across different tissues remain largely unknown. Accordingly, the mechanisms underlying macro- and micro-vascular endothelial senescence vary in different pathophysiological conditions, thus offering specific target(s) for therapeutic development of senolytic drugs.

Gastrodin alleviates premature senescence of vascular endothelial cells by enhancing the Nrf2/HO-1 signalling pathway

Endothelial dysfunction is an independent risk factor for stroke. The dysfunction of endothelial cells (EC) is closely concerned with EC senescence. Gastrodin (GAS) is an organic compound extracted from the dried root mass of the Orchidaceae plant Gastrodiae gastrodiae. It is used clinically to treat diseases such as vertebrobasilar insufficiency, vestibular neuronitis and vertigo. In the present study, we used hydrogen peroxide (H2 O2 )-induced human umbilical vein endothelial cells (HUVECs) to establish an in vitro EC senescence model and to investigate the role and mechanism of GAS in EC senescence. It's found that H2 O2 -treated HUVECs increased the proportion of senescence-associated β-galactosidase (SA β-gal) positive cells and the relative protein expression levels of senescence-associated cyclin p16 and p21. In addition, GAS reduced the proportion of SA β-gal positive cells and the relative protein expression levels of p16 and p21, and increased the proliferation and migration ability of HUVECs. Meanwhile, GAS increased the expression of the anti-oxidative stress protein HO-1 and its nuclear expression level of Nrf2. The anti-senescence effect of GAS was blocked when HO-1 expression was inhibited by SnPPIX. Furthermore, absence of HO-1 abolished the effect of GAS on HUVEC proliferation and migration. In conclusion, GAS ameliorated H2 O2 -induced cellular senescence and enhanced cell proliferation and migration by enhancing Nrf2/HO-1 signalling in HUVECs. These findings of our study expanded the understanding of GAS pharmacology and suggested that GAS may offer a potential therapeutic agent for stroke.

Endothelial senescence alleviates cognitive impairment in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is among the most prevalent age-related neurodegenerative diseases. Endothelial cell (EC) senescence was discovered in the AD brain, but its function in AD pathogenesis was unidentified. Here we created an AD mouse model with EC senescence (APP/PS1;TERF2DN mice) by intercrossing APP/PS1 mice with Tie2 promoter-driven dominant negative telomeric repeat-binding factor 2 transgenic mice (TERF2DN-Tg mice). We evaluated cognitive functions and AD brain pathology in APP/PS1;TERF2DN mice. Surprisingly, compared with the control APP/PS1 mice, APP/PS1;TERF2DN mice demonstrated the attenuation of cognitive impairment and amyloid-β (Aβ) pathology, accompanied by the compaction of Aβ plaques with increased microglial coverage and reduced neurite dystrophy. Moreover, we evaluated whether EC senescence could affect microglial morphology and phagocytosis of Aβ. Compared with wild-type mice, microglia in TERF2DN-Tg mice display increased numbers of endpoints (a morphometric parameter to quantify the number of processes) and Aβ phagocytosis and related gene expression. Single-cell RNA-sequencing analysis showed that compared with APP/PS1 mouse microglia, APP/PS1;TERF2DN mouse microglia displayed a modest decline in disease-associated microglia, accompanied by an altered direction of biological process branching from antigen synthesis and arrangement to ribonucleoprotein complex biogenesis. Our outcomes indicate that EC senescence alters microglia toward a protective phenotype with a rise in phagocytic and barrier roles, and may offer a clue to create a novel preventive/therapeutic method to treat AD.

Astaxanthin enhances autophagy, amyloid beta clearance and exerts anti-inflammatory effects in in vitro models of Alzheimer's disease-related blood brain barrier dysfunction and inflammation

Defective degradation and clearance of amyloid-β as well as inflammation per se are crucial players in the pathology of Alzheimer's disease (AD). A defective transport across the blood-brain barrier is causative for amyloid-β (Aβ) accumulation in the brain, provoking amyloid plaque formation. Using primary porcine brain capillary endothelial cells and murine organotypic hippocampal slice cultures as in vitro models of AD, we investigated the effects of the antioxidant astaxanthin (ASX) on Aβ clearance and neuroinflammation. We report that ASX enhanced the clearance of misfolded proteins in primary porcine brain capillary endothelial cells by inducing autophagy and altered the Aβ processing pathway. We observed a reduction in the expression levels of intracellular and secreted amyloid precursor protein/Aβ accompanied by an increase in ABC transporters ABCA1, ABCG1 as well as low density lipoprotein receptor-related protein 1 mRNA levels. Furthermore, ASX treatment increased autophagic flux as evidenced by increased lipidation of LC3B-II as well as reduced protein expression of phosphorylated S6 ribosomal protein and mTOR. In LPS-stimulated brain slices, ASX exerted anti-inflammatory effects by reducing the secretion of inflammatory cytokines while shifting microglia polarization from M1 to M2 phenotype. Our data suggest ASX as potential therapeutic compound ameliorating AD-related blood brain barrier impairment and inflammation.

Soluble guanylyl cyclase: A novel target for the treatment of vascular cognitive impairment?

Vascular cognitive impairment (VCI) describes neurodegenerative disorders characterized by a vascular component. Pathologically, it involves decreased cerebral blood flow (CBF), white matter lesions, endothelial dysfunction, and blood-brain barrier (BBB) impairments. Molecularly, oxidative stress and inflammation are two of the major underlying mechanisms. Nitric oxide (NO) physiologically stimulates soluble guanylate cyclase (sGC) to induce cGMP production. However, under pathological conditions, NO seems to be at the basis of oxidative stress and inflammation, leading to a decrease in sGC activity and expression. The native form of sGC needs a ferrous heme group bound in order to be sensitive to NO (Fe(II)sGC). Oxidation of sGC leads to the conversion of ferrous to ferric heme (Fe(III)sGC) and even heme-loss (apo-sGC). Both Fe(III)sGC and apo-sGC are insensitive to NO, and the enzyme is therefore inactive. sGC activity can be enhanced either by targeting the NO-sensitive native sGC (Fe(II)sGC), or the inactive, oxidized sGC (Fe(III)sGC) and the heme-free apo-sGC. For this purpose, sGC stimulators acting on Fe(II)sGC and sGC activators acting on Fe(III)sGC/apo-sGC have been developed. These sGC agonists have shown their efficacy in cardiovascular diseases by restoring the physiological and protective functions of the NO-sGC-cGMP pathway, including the reduction of oxidative stress and inflammation, and improvement of vascular functioning. Yet, only very little research has been performed within the cerebrovascular system and VCI pathology when focusing on sGC modulation and its potential protective mechanisms on vascular and neural function. Therefore, within this review, the potential of sGC as a target for treating VCI is highlighted.

Identification and functional analysis of senescent cells in the cardiovascular system using omics approaches

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide, and senescent cells have emerged as key contributors to its pathogenesis. Senescent cells exhibit cell cycle arrest and secrete a range of proinflammatory factors, termed the senescence-associated secretory phenotype (SASP), which promotes tissue dysfunction and exacerbates CVD progression. Omics technologies, specifically transcriptomics and proteomics, offer powerful tools to uncover and define the molecular signatures of senescent cells in cardiovascular tissue. By analyzing the comprehensive molecular profiles of senescent cells, omics approaches can identify specific genetic alterations, gene expression patterns, protein abundances, and metabolite levels associated with senescence in CVD. These omics-based discoveries provide insights into the mechanisms underlying senescence-induced cardiovascular damage, facilitating the development of novel diagnostic biomarkers and therapeutic targets. Furthermore, integration of multiple omics data sets enables a systems-level understanding of senescence in CVD, paving the way for precision medicine approaches to prevent or treat cardiovascular aging and its associated complications.

Iron overload induces cerebral endothelial senescence in aged mice and in primary culture in a sex-dependent manner

Iron imbalance in the brain negatively affects brain function. With aging, iron levels increase in the brain and contribute to brain damage and neurological disorders. Changes in the cerebral vasculature with aging may enhance iron entry into the brain parenchyma, leading to iron overload and its deleterious consequences. Endothelial senescence has emerged as an important contributor to age-related changes in the cerebral vasculature. Evidence indicates that iron overload may induce senescence in cultured cell lines. Importantly, cells derived from female human and mice generally show enhanced senescence-associated phenotype, compared with males. Thus, we hypothesize that cerebral endothelial cells (CEC) derived from aged female mice are more susceptible to iron-induced senescence, compared with CEC from aged males. We found that aged female mice, but not males, showed cognitive deficits when chronically treated with ferric citrate (FC), and their brains and the brain vasculature showed senescence-associated phenotype. We also found that primary culture of CEC derived from aged female mice, but not male-derived CEC, exhibited senescence-associated phenotype when treated with FC. We identified that the transmembrane receptor Robo4 was downregulated in the brain vasculature and in cultured primary CEC derived from aged female mice, compared with those from male mice. We discovered that Robo4 downregulation contributed to enhanced vulnerability to FC-induced senescence. Thus, our study identifies Robo4 downregulation as a driver of senescence induced by iron overload in primary culture of CEC and a potential risk factor of brain vasculature impairment and brain dysfunction.

Vascular Ageing: Mechanisms, Risk Factors, and Treatment Strategies

Ageing constitutes the biggest risk factor for poor health and adversely affects the integrity and function of all the cells, tissues, and organs in the human body. Vascular ageing, characterised by vascular stiffness, endothelial dysfunction, increased oxidative stress, chronic low-grade inflammation, and early-stage atherosclerosis, may trigger or exacerbate the development of age-related vascular diseases, which each year contribute to more than 3.8 million deaths in Europe alone and necessitate a better understanding of the mechanisms involved. To this end, a large number of recent preclinical and clinical studies have focused on the exponential accumulation of senescent cells in the vascular system and paid particular attention to the specific roles of senescence-associated secretory phenotype, proteostasis dysfunction, age-mediated modulation of certain microRNA (miRNAs), and the contribution of other major vascular risk factors, notably diabetes, hypertension, or smoking, to vascular ageing in the elderly. The data generated paved the way for the development of various senotherapeutic interventions, ranging from the application of synthetic or natural senolytics and senomorphics to attempt to modify lifestyle, control diet, and restrict calorie intake. However, specific guidelines, considering the severity and characteristics of vascular ageing, need to be established before widespread use of these agents. This review briefly discusses the molecular and cellular mechanisms of vascular ageing and summarises the efficacy of widely studied senotherapeutics in the context of vascular ageing.

CRTC1 is a potential target to delay aging-induced cognitive deficit by protecting the integrity of the blood-brain barrier via inhibiting inflammation

Aging can cause attenuation in the functioning of multiple organs, and blood-brain barrier (BBB) breakdown could promote the occurrence of disorders of the central nervous system during aging. Since inflammation is considered to be an important factor underlying BBB injury during aging, vascular endothelial cell senescence serves as a critical pathological basis for the destruction of BBB integrity. In the current review, we have first introduced the concepts related to aging-induced cognitive deficit and BBB integrity damage. Thereafter, we reviewed the potential relationship between disruption of BBB integrity and cognition deficit and the role of inflammation, vascular endothelial cell senescence, and BBB injury. We have also briefly introduced the function of CREB-regulated transcription co-activator 1 (CRTC1) in cognition and aging-induced CRTC1 changes as well as the critical roles of CRTC1/cyclooxygenase-2 (COX-2) in regulating inflammation, endothelial cell senescence, and BBB injury. Finally, the underlying mechanisms have been summarized and we propose that CRTC1 could be a promising target to delay aging-induced cognitive deficit by protecting the integrity of BBB through promoting inhibition of inflammation-mediated endothelial cell senescence.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Recent advances in arterial spin labeling perfusion MRI in patients with vascular cognitive impairment

Cognitive impairment (CI) is a major health concern in aging populations. It impairs patients' independent life and may progress to dementia. Vascular cognitive impairment (VCI) encompasses all cerebrovascular pathologies that contribute to cognitive impairment (CI). Moreover, the majority of CI subtypes involve various aspects of vascular dysfunction. Recent research highlights the critical role of reduced cerebral blood flow (CBF) in the progress of VCI, and the detection of altered CBF may help to detect or even predict the onset of VCI. Arterial spin labeling (ASL) is a non-invasive, non-ionizing perfusion MRI technique for assessing CBF qualitatively and quantitatively. Recent methodological advances enabling improved signal-to-noise ratio (SNR) and data acquisition have led to an increase in the use of ASL to assess CBF in VCI patients. Combined with other imaging modalities and biomarkers, ASL has great potential for identifying early VCI and guiding prediction and prevention strategies. This review focuses on recent advances in ASL-based perfusion MRI for identifying patients at high risk of VCI.

Inducible Pluripotent Stem Cell-Derived Small Extracellular Vesicles Rejuvenate Senescent Blood-Brain Barrier to Protect against Ischemic Stroke in Aged Mice

Blood-brain barrier (BBB) breakdown after ischemic stroke exacerbates brain injury and BBB senescence can cause severe neurological deficits in aged ischemic stroke population. Recent evidence reveals that inducible pluripotent stem cell-derived small extracellular vesicles (iPSC-sEVs) possess phenomenal antisenescence capability. However, whether iPSC-sEVs can rejuvenate BBB senescence to improve stroke outcomes in aged mice remains unknown. Here, we showed that long-term treatment with iPSC-sEVs alleviated aging-induced BBB senescence in aged mice. In aged stroke mice, iPSC-sEVs significantly mitigated BBB integrity damage, reduced the following infiltration of peripheral leukocytes, and decreased the release of pro-inflammatory factors from the leukocytes, which ultimately inhibited neuronal death and improved neurofunctional recovery. Mechanism studies showed that iPSC-sEVs could activate the endothelial nitric oxide synthase (eNOS) and up-regulate sirtuin 1 (Sirt1) in senescent endothelial cells. Blocking the activation of eNOS abolished iPSC-sEV-mediated rejuvenation of BBB senescence and the protection of BBB integrity. Proteomics results demonstrated that iPSC-sEVs were enriched with bioactive factors including AKT serine/threonine kinase 1 (AKT1) and calmodulin (CALM) to activate the eNOS-Sirt1 axis. Further investigation showed that AKT1 and CALM inhibitors blocked iPSC-sEV-afforded activation of the eNOS-Sirt1 axis in senescent endothelial cells. Taken together, iPSC-sEVs can protect against ischemic stroke in aged mice by rejuvenating BBB senescence, partially, through delivering AKT1 and CALM to activate eNOS-Sirt1 axis, which indicates that iPSC-sEVs treatment is an effective alternative to treat ischemic stroke in the aged population.

Endothelial senescence in vascular diseases: current understanding and future opportunities in senotherapeutics

Senescence compromises the essential role that the endothelium plays in maintaining vascular homeostasis, so promoting endothelial dysfunction and the development of age-related vascular diseases. Their biological and clinical significance calls for strategies for identifying and therapeutically targeting senescent endothelial cells. While senescence and endothelial dysfunction have been studied extensively, distinguishing what is distinctly endothelial senescence remains a barrier to overcome for an effective approach to addressing it. Here, we review the mechanisms underlying endothelial senescence and the evidence for its clinical importance. Furthermore, we discuss the current state and the limitations in the approaches for the detection and therapeutic intervention of target cells, suggesting potential directions for future research.

A Unified Model of Age-Related Cardiovascular Disease

Despite progress in biomedical technologies, cardiovascular disease remains the main cause of mortality. This is at least in part because current clinical interventions do not adequately take into account aging as a driver and are hence aimed at suboptimal targets. To achieve progress, consideration needs to be given to the role of cell aging in disease pathogenesis. We propose a model unifying the fundamental processes underlying most age-associated cardiovascular pathologies. According to this model, cell aging, leading to cell senescence, is responsible for tissue changes leading to age-related cardiovascular disease. This process, occurring due to telomerase inactivation and telomere attrition, affects all components of the cardiovascular system, including cardiomyocytes, vascular endothelial cells, smooth muscle cells, cardiac fibroblasts, and immune cells. The unified model offers insights into the relationship between upstream risk factors and downstream clinical outcomes and explains why interventions aimed at either of these components have limited success. Potential therapeutic approaches are considered based on this model. Because telomerase activity can prevent and reverse cell senescence, telomerase gene therapy is discussed as a promising intervention. Telomerase gene therapy and similar systems interventions based on the unified model are expected to be transformational in cardiovascular medicine.

Endothelin A receptors contribute to senescence of brain microvascular endothelial cells

Cellular senescence plays a pivotal role in the aging and progression of neurodegenerative diseases, including vascular cognitive impairment and dementia (VCID). In postmortem brains from individuals with VCID, endothelin-1 (ET-1) levels closely correlate with blood barrier breakdown and cerebral hypoperfusion. Brain microvascular endothelial cells (BMVECs), previously thought to have exclusively endothelin B receptors, also possess endothelin A (ETA) receptors; however, the functional significance of this receptor in BMVECs is not known. We hypothesize that ETA receptors mediate BMVEC senescence. Serum-starved human BMVECs (HBEC5i) were incubated with ET-1 (1 µmol/L) in the presence/absence of ETA receptor antagonist BQ-123 (20 µmol/L). Cells were collected for Western blot and quantitative real-time PCR analyses. Treatment of ET-1 increased protein expression of ETA receptor, while it was prevented by the ETA receptor antagonist. ET-1 increased p21, p16, p53, LIF1 and cyclin D1 protein levels, and β-galactosidase accumulation, which were prevented in the presence of ETA blockade. While there was no change in tight junction proteins, ET-1 decreased adherent junction protein vascular endothelial cadherin (VE-cadherin) levels. In conclusion, ET-1 upregulates ETA receptors in BMVECs in an autocrine manner and triggers the activation of senescence. These in vitro findings need to be further studied in vivo to establish the role of ETA receptors in the progression of endothelial senescence in VCID.

Dysfunction of the neurovascular unit in brain aging

An emerging concept termed the neurovascular unit (NVU) underlines neurovascular coupling. It has been reported that NVU impairment can result in neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Aging is a complex and irreversible process caused by programmed and damage-related factors. Loss of biological functions and increased susceptibility to additional neurodegenerative diseases are major characteristics of aging. In this review, we describe the basics of the NVU and discuss the effect of aging on NVU basics. Furthermore, we summarize the mechanisms that increase NVU susceptibility to neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Finally, we discuss new treatments for neurodegenerative diseases and methods of maintaining an intact NVU that may delay or diminish aging.

The intersection between toxicology and aging research: A toxic aging coin perspective

We are imminently faced with the challenges of an increasingly aging population and longer lifespans due to improved health care. Concomitantly, we are faced with ubiquitous environmental pollution linked with various health effects and age-related diseases which contribute to increased morbidity with age. Geriatric populations are rarely considered in the development of environmental regulations or in toxicology research. Today, life expectancy is often into one's 80s or beyond, which means multiple decades living as a geriatric individual. Hence, adverse health effects and late-onset diseases might be due to environmental exposures as a geriatric, and we currently have no way of knowing. Considering aging from a different perspective, the term "gerontogen" was coined in 1987 to describe chemicals that accelerate biological aging but has largely been left out of toxicology research. Thus, we are challenged with a two-faced problem that we can describe as a "toxic aging coin"; on one side we consider how age affects the toxic outcome of chemicals, whereas on the other side we consider how chemicals accelerate aging (i.e. how chemicals act as gerontogens). Conveniently, both sides of this coin can be tackled with a single animal study that considers multiple age groups and assesses basic toxicology of the chemical(s) tested and aging-focused endpoints. Here, I introduce the concept of this toxic aging coin and some key considerations for how it applies to toxicology research. My discussion of this concept will focus on the brain, my area of expertise, but could be translated to any organ system.

Soluble guanylate cyclase stimulator riociguat improves spatial memory in mice via peripheral mechanisms

Soluble guanylate cyclase (sGC) - cyclic guanosine monophosphate (cGMP) signalling is important for healthy memory function and a healthy vascular system. Targeting sGC-cGMP signalling can therefore be a potential strategy to enhance memory processes. sGC can be targeted by using agonists, such as sGC stimulator riociguat. Therefore, this study aimed to target sGC using riociguat to investigate its acute effects on memory function and neuronal plasticity in mice. The effects of riociguat on long-term memory and a biperiden-induced memory deficit model for assessing short-term memory were tested in the object location task, and working memory was tested in the Y-maze continuous alternation task. Pharmacokinetic measurements were performed within brain tissue of mice, and hippocampal plasticity measures were assessed using western blotting. Acute oral administration with a low dose of 0.03 mg/kg riociguat was able to enhance working-, short-, and long-term spatial memory. Under cerebral vasoconstriction higher doses of riociguat were still effective on memory. Pharmacokinetic measurements revealed poor brain penetration of riociguat and its metabolite M-1. Increased activation of VASP was found, while no effects were found on other memory-related hippocampal plasticity measures. Memory enhancing effects of riociguat are most likely regulated by vascular peripheral effects on cGMP signalling. Yet, further research is needed to investigate the possible contribution of hemodynamic or metabolic effects of sGC stimulators on memory performance.

Aging related impairment of brain microvascular bioenergetics involves oxidative phosphorylation and glycolytic pathways

Mitochondrial and glycolytic energy pathways regulate the vascular functions. Aging impairs the cerebrovascular function and increases the risk of stroke and cognitive dysfunction. The goal of our study is to characterize the impact of aging on brain microvascular energetics. We measured the oxygen consumption and extracellular acidification rates of freshly isolated brain microvessels (BMVs) from young (2-4 months) and aged (20-22 months) C57Bl/6 male mice. Cellular ATP production in BMVs was predominantly dependent on oxidative phosphorylation (OXPHOS) with glucose as the preferred energy substrate. Aged BMVs exhibit lower ATP production rate with diminished OXPHOS and glycolytic rate accompanied by increased utilization of glutamine. Impairments of glycolysis displayed by aged BMVs included reduced compensatory glycolysis whereas impairments of mitochondrial respiration involved reduction of spare respiratory capacity and proton leak. Aged BMVs showed reduced levels of key glycolysis proteins including glucose transporter 1 and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 but normal lactate dehydrogenase activity. Mitochondrial protein levels were mostly unchanged whereas citrate synthase activity was reduced, and glutamate dehydrogenase was increased in aged BMVs. Thus, for the first time, we identified the dominant role of mitochondria in bioenergetics of BMVs and the alterations of the energy pathways that make the aged BMVs vulnerable to injury.

Glycolytic and Oxidative Phosphorylation Defects Precede the Development of Senescence in Primary Human Brain Microvascular Endothelial Cells

Alterations of mitochondrial and glycolytic energy pathways related to aging could contribute to cerebrovascular dysfunction. We studied the impact of aging on energetics of primary human brain microvascular endothelial cells (HBMECs) by comparing the young (passages 7-9), pre-senescent (passages 13-15), and senescent (passages 20-21) cells. Pre-senescent HBMECs displayed decreased telomere length and undetectable telomerase activity although markers of senescence were unaffected. Bioenergetics in HBMECs were determined by measuring the oxygen consumption (OCR) and extracellular acidification (ECAR) rates. Cellular ATP production in young HBMECs was predominantly dependent on glycolysis with glutamine as the preferred fuel for mitochondrial oxidative phosphorylation (OXPHOS). In contrast, pre-senescent HBMECs displayed equal contribution to ATP production rate from glycolysis and OXPHOS with equal utilization of glutamine, glucose, and fatty acids as mitofuels. Compared to young, pre-senescent HBMECs showed a lower overall ATP production rate that was characterized by diminished contribution from glycolysis. Impairments of glycolysis displayed by pre-senescent cells included reduced basal glycolysis, compensatory glycolysis, and non-glycolytic acidification. Furthermore, impairments of mitochondrial respiration in pre-senescent cells involved the reduction of maximal respiration and spare respiratory capacity but intact basal and ATP production-related OCR. Proton leak and non-mitochondrial respiration, however, were unchanged in the pre-senescent HBMECs. HBMECS at passages 20-21 displayed expression of senescence markers and continued similar defects in glycolysis and worsened OXPHOS. Thus, for the first time, we characterized the bioenergetics of pre-senescent HBMECs comprehensively to identify the alterations of the energy pathways that could contribute to aging.

Modulation of High-Fat Diet-Induced Brain Oxidative Stress by Ferulate-Rich Germinated Brown Rice Ethyl Acetate Extract

The oxidative stress resulting from the production of reactive oxygen species plays a vital role in inflammatory processes and is associated with neurodegenerative changes. In view of the ability of germinated brown rice (GBR) to improve learning and memory, this present study aimed to investigate the mechanistic basis of GBR’s neuroprotection in a high-fat diet (HFD)-induced oxidative changes in adult Sprague–Dawley rats. Ferulate-rich GBR ethyl acetate extract (GBR-EA; 100 mg/kg and 200 mg/kg body weight) was supplemented orally for the last 3 months of 6 months HFD feeding during the study. GBR-EA supplementation was found to improve lipid profile and serum antioxidant status, when compared to the HFD group. Elevated mRNA expressions of SOD1, SOD2, SOD3, Catalase, and GPX were demonstrated in the frontal cortex and hippocampus of GBR-EA treated animals. The pro-inflammatory changes induced by HFD in the hippocampus were attenuated by GBR-EA through the downregulation of CRP and TNF- α and upregulation of PPAR-γ. GBR also reduced the hippocampal mRNA expression and enzyme level of acetylcholinesterase. In conclusion, this study proposed the possible transcriptomic regulation of antioxidant and inflammation in neurodegenerative processes resulting from high cholesterol consumption, with an emphasis on GBR’s potential to ameliorate such changes.

Delay of endothelial cell senescence protects cerebral barrier against age-related dysfunction: role of senolytics and senomorphics

Accumulation of senescent cells in cerebrovasculature is thought to play an important role in age-related disruption of blood-brain barrier (BBB). Using an in vitro model of human BBB, composed of brain microvascular endothelial cells (BMECs), astrocytes and pericytes, this study explored the so-called correlative link between BMEC senescence and the BBB dysfunction in the absence or presence of functionally distinct senotherapeutics. Replicative senescence was deemed present at passage ≥19 where BMECs displayed shortened telomere length, reduced proliferative and tubulogenic potentials and increased NADPH oxidase activity, superoxide anion production (markers of oxidative stress), S-β-galactosidase activity and γ-H2AX staining. Significant impairments observed in integrity and function of a model of BBB established with senescent BMECs, ascertained successively by decreases in transendothelial electrical resistance and increases in paracellular flux, revealed a close correlation between endothelial cell senescence and BBB dysfunction. Disruptions in the localization or expression of tight junction proteins, zonula occludens-1, occludin, and claudin-5 in senescent BMECs somewhat explained this dysfunction. Indeed, treatment of relatively old BMEC (passage 16) with a cocktail of senolytics (dasatinib and quercetin) or senomorphics targeting transcription factor NF-κB (QNZ), p38MAPK signaling pathway (BIRB-796) or pro-oxidant enzyme NADPH oxidase (VAS2870) until passage 20 rendered these cells more resistant to senescence and totally preserved BBB characteristics by restoring subcellular localization and expression of tight junction proteins. In conclusion, attempts that effectively mitigate accumulation of senescent endothelial cells in cerebrovasculature may prevent age-related BBB dysfunction and may be of prophylactic or therapeutic value to extend lifelong health and wellbeing.

Connecting aging biology and inflammation in the omics era

Aging is characterized by the accumulation of damage to macromolecules and cell architecture that triggers a proinflammatory state in blood and solid tissues, termed inflammaging. Inflammaging has been implicated in the pathogenesis of many age-associated chronic diseases as well as loss of physical and cognitive function. The search for mechanisms that underlie inflammaging focused initially on the hallmarks of aging, but it is rapidly expanding in multiple directions. Here, we discuss the threads connecting cellular senescence and mitochondrial dysfunction to impaired mitophagy and DNA damage, which may act as a hub for inflammaging. We explore the emerging multi-omics efforts that aspire to define the complexity of inflammaging - and identify molecular signatures and novel targets for interventions aimed at counteracting excessive inflammation and its deleterious consequences while preserving the physiological immune response. Finally, we review the emerging evidence that inflammation is involved in brain aging and neurodegenerative diseases. Our goal is to broaden the research agenda for inflammaging with an eye on new therapeutic opportunities.

Historical and current perspectives on blood endothelial cell heterogeneity in the brain

Dynamic brain activity requires timely communications between the brain parenchyma and circulating blood. Brain-blood communication is facilitated by intricate networks of brain vasculature, which display striking heterogeneity in structure and function. This vascular cell heterogeneity in the brain is fundamental to mediating diverse brain functions and has long been recognized. However, the molecular basis of this biological phenomenon has only recently begun to be elucidated. Over the past century, various animal species and in vitro systems have contributed to the accumulation of our fundamental and phylogenetic knowledge about brain vasculature, collectively advancing this research field. Historically, dye tracer and microscopic observations have provided valuable insights into the anatomical and functional properties of vasculature across the brain, and these techniques remain an important approach. Additionally, recent advances in molecular genetics and omics technologies have revealed significant molecular heterogeneity within brain endothelial and perivascular cell types. The combination of these conventional and modern approaches has enabled us to identify phenotypic differences between healthy and abnormal conditions at the single-cell level. Accordingly, our understanding of brain vascular cell states during physiological, pathological, and aging processes has rapidly expanded. In this review, we summarize major historical advances and current knowledge on blood endothelial cell heterogeneity in the brain, and discuss important unsolved questions in the field.

Age-Related Midbrain Inflammation and Senescence in Parkinson’s Disease

Immune responses are arising as a common feature of several neurodegenerative diseases, such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and Amyotrophic Lateral Sclerosis (ALS), but their role as either causative or consequential remains debated. It is evident that there is local inflammation in the midbrain in PD patients even before symptom onset, but the underlying mechanisms remain elusive. In this mini-review, we discuss this midbrain inflammation in the context of PD and argue that cellular senescence may be the cause for this immune response. We postulate that to unravel the relationship between inflammation and senescence in PD, it is crucial to first understand the potential causative roles of various cell types of the midbrain and determine how the possible paracrine spreading of senescence between them may lead to observed local immune responses. We hypothesize that secretion of pro-inflammatory factors by senescent cells in the midbrain triggers neuroinflammation resulting in immune cell-mediated killing of midbrain dopaminergic (DA) neurons in PD.

The Potential of Dietary Bioactive Compounds against SARS-CoV-2 and COVID-19-Induced Endothelial Dysfunction

COVID-19 is an endothelial disease. All the major comorbidities that increase the risk for severe SARS-CoV-2 infection and severe COVID-19 including old age, obesity, diabetes, hypertension, respiratory disease, compromised immune system, coronary artery disease or heart failure are associated with dysfunctional endothelium. Genetics and environmental factors (epigenetics) are major risk factors for endothelial dysfunction. Individuals with metabolic syndrome are at increased risk for severe SARS-CoV-2 infection and poor COVID-19 outcomes and higher risk of mortality. Old age is a non-modifiable risk factor. All other risk factors are modifiable. This review also identifies dietary risk factors for endothelial dysfunction. Potential dietary preventions that address endothelial dysfunction and its sequelae may have an important role in preventing SARS-CoV-2 infection severity and are key factors for future research to address. This review presents some dietary bioactives with demonstrated efficacy against dysfunctional endothelial cells. This review also covers dietary bioactives with efficacy against SARS-CoV-2 infection. Dietary bioactive compounds that prevent endothelial dysfunction and its sequelae, especially in the gastrointestinal tract, will result in more effective prevention of SARS-CoV-2 variant infection severity and are key factors for future food research to address.

Tetrahydroxy stilbene glycoside attenuates endothelial cell premature senescence induced by H2O2 through the microRNA-34a/SIRT1 pathway

Numerous studies have demonstrated that endothelial cell senescence plays a decisive role in the development and progression of cardiovascular diseases (CVD). Our previous results confirmed that Tetrahydroxy stilbene glycoside (TSG) can alleviate the human umbilical vein endothelial cells (HUVECs) senescence induced by H₂O₂ through SIRT1. It has been reported that miR-34a is a translational suppressor of SIRT1. In this study, we aimed to explore whether TSG regulates SIRT1 through miR-34a to ameliorate HUVECs senescence. H₂O₂ was used to induce premature senescence in HUVECs, and miR-34a mimic or inhibitor were transfected to over-express or suppress the expression level of miR-34a. Results revealed that TSG apparently decreased the miR-34a expression level in H₂O₂-induced premature senescence of HUVECs. When SIRT1 expression was inhibited by EX527, the attenuation of TSG on the expression level of miR-34a were abolished. When miR-34a expression was knockdown, the effect of TSG on HUVECs senescence could be enhanced. While miR-34a mimic could reverse the effect of TSG on HUVECs senescence. In conclusion, we demonstrated that TSG could attenuated endothelial cell senescence by targeting miR-34a/SIRT1 pathway.

G-quadruplexes Stabilization Upregulates CCN1 and Accelerates Aging in Cultured Cerebral Endothelial Cells

Senescence in the cerebral endothelium has been proposed as a mechanism that can drive dysfunction of the cerebral vasculature, which precedes vascular dementia. Cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) is a matricellular protein secreted by cerebral endothelial cells (CEC). CCN1 induces senescence in fibroblasts. However, whether CCN1 contributes to senescence in CEC and how this is regulated requires further study. Aging has been associated with the formation of four-stranded Guanine-quadruplexes (G4s) in G-rich motifs of DNA and RNA. Stabilization of the G4 structures regulates transcription and translation either by upregulation or downregulation depending on the gene target. Previously, we showed that aged mice treated with a G4-stabilizing compound had enhanced senescence-associated (SA) phenotypes in their brains, and these mice exhibited enhanced cognitive deficits. A sequence in the 3'-UTR of the human CCN1 mRNA has the ability to fold into G4s in vitro. We hypothesize that G4 stabilization regulates CCN1 in cultured primary CEC and induces endothelial senescence. We used cerebral microvessel fractions and cultured primary CEC from young (4-months old, m/o) and aged (18-m/o) mice to determine CCN1 levels. SA phenotypes were determined by high-resolution fluorescence microscopy in cultured primary CEC, and we used Thioflavin T to recognize RNA-G4s for fluorescence spectra. We found that cultured CEC from aged mice exhibited enhanced levels of SA phenotypes, and higher levels of CCN1 and G4 stabilization. In cultured CEC, CCN1 induced SA phenotypes, such as SA β-galactosidase activity, and double-strand DNA damage. Furthermore, CCN1 levels were upregulated by a G4 ligand, and a G-rich motif in the 3'-UTR of the Ccn1 mRNA was folded into a G4. In conclusion, we demonstrate that CCN1 can induce senescence in cultured primary CEC, and we provide evidence that G4 stabilization is a novel mechanism regulating the SASP component CCN1.

lncRNA HOTAIR mediates OGD/R-induced cell injury and angiogenesis in a EZH2-dependent manner

Long non-coding RNAs (lncRNA) serve an important role in neonatal hypoxic-ischemic encephalopathy (HIE) have been reported to regulate the activity of HIE-associated proteins. The present study aimed to elucidate the role of Hox transcript antisense intergenic RNA (HOTAIR) in oxygen-glucose deprivation/reperfusion (OGD/R)-induced injury in human brain microvascular endothelial cells (hBMVECs). The levels of HOTAIR were evaluated in the serum of neonatal patients with HIE, and the effects of HOTAIR were evaluated using in vitro assays, such as reverse transcription-quantitative PCR to detect lncRNA and mRNA levels and western blot analysis to determine protein levels. Moreover, RNA immunoprecipitation assays were used to evaluate the association between HOTAIR and enhancer of zeste homolog 2 (EZH2), Cell Counting Kit-8 was used to detect cell viability, an endothelial monolayer cell permeability assay was used to analyze cell viability, TUNEL staining was used to detect the levels of apoptosis, a Transwell assay was used to evaluate cell invasion and a tube formation assay was used to analyze tube formation ability. In addition, the effects of HOTAIR and EZH2 on cell apoptosis and the invasive and tube formation abilities of hBMVECs were investigated using TUNEL, Transwell and tube formation assays, respectively. The results showed that the expression levels of HOTAIR were markedly increased both in neonatal HIE patients and in the OGD/R injury in vitro model. HOTAIR knockdown reduced hBMVEC viability, enhanced cell permeability and apoptosis, in addition to decreasing the expression levels of tight junction-related proteins, such as zonula occludens-1, occluden, Claudin5 and vascular endothelial-cadherin. However, EZH2 overexpression reversed the effects of HOTAIR silencing on hBMVECs. Additionally, HOTAIR knockdown enhanced the migratory and tube formation abilities of OGD/R-induced hBMVECs, which were also reversed by EZH2 overexpression. Overall, the present study revealed an association between the HOTAIR/EZH2 axis and brain microvascular endothelial cell injury and angiogenesis, which provides a novel insight into the molecular mechanism underlying stroke or the development of new pharmacotherapies.

Age-related immune alterations and cerebrovascular inflammation

Aging is associated with chronic systemic inflammation, which contributes to the development of many age-related diseases, including vascular disease. The world's population is aging, leading to an increasing prevalence of both stroke and vascular dementia. The inflammatory response to ischemic stroke is critical to both stroke pathophysiology and recovery. Age is a predictor of poor outcomes after stroke. The immune response to stroke is altered in aged individuals, which contributes to the disparate outcomes between young and aged patients. In this review, we describe the current knowledge of the effects of aging on the immune system and the cerebral vasculature and how these changes alter the immune response to stroke and vascular dementia in animal and human studies. Potential implications of these age-related immune alterations on chronic inflammation in vascular disease outcome are highlighted.

High fat diet-induced brain damaging effects through autophagy-mediated senescence, inflammation and apoptosis mitigated by ginsenoside F1-enhanced mixture

Background

Herbal medicines are popular approaches to capably prevent and treat obesity and its related diseases. Excessive exposure to dietary lipids causes oxidative stress and inflammation, which possibly induces cellular senescence and contribute the damaging effects in brain. The potential roles of selective enhanced ginsenoside in regulating high fat diet (HFD)-induced brain damage remain unknown.

Methods

The protection function of Ginsenoside F1-enhanced mixture (SGB121) was evaluated by in vivo and in vitro experiments. Human primary astrocytes and SH-SY5Y cells were treated with palmitic acid conjugated Bovine Serum Albumin, and the effects of SGB121 were determined by MTT and lipid uptake assays. For in vivo tests, C57BL/6J mice were fed with high fat diet for 3 months with or without SGB121 administration. Thereafter, immunohistochemistry, western blot, PCR and ELISA assays were conducted with brain tissues.

Results and conclusion

SGB121 selectively suppressed HFD-induced oxidative stress and cellular senescence in brain, and reduced subsequent inflammation responses manifested by abrogated secretion of IL-6, IL-1β and TNFα via NF-κB signaling pathway. Interestingly, SGB121 protects against HFD-induced damage by improving mitophagy and endoplasmic reticulum-stress associated autophagy flux and inhibiting apoptosis. In addition, SGB121 regulates lipid uptake and accumulation by FATP4 and PPARα. SGB121 significantly abates excessively phosphorylated tau protein in the cortex and GFAP activation in corpus callosum. Together, our results suggest that SGB121 is able to favor the resistance of brain to HFD-induced damage, therefore provide explicit evidence of the potential to be a functional food.

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High fat diet induces oxidative stress and subsequent cellular senescence in mice brain.

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High fat diet induces pathologies in cortex and GFAP activation in corpus callosum.

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Ginsenoside F1-enhanced mixture ameliorates damaging effect by modulating autophagy flux and inflammation.

Inflammation and Oxidative Stress: Potential Targets for Improving Prognosis After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) has a high mortality rate and causes long-term disability in many patients, often associated with cognitive impairment. However, the pathogenesis of delayed brain dysfunction after SAH is not fully understood. A growing body of evidence suggests that neuroinflammation and oxidative stress play a negative role in neurofunctional deficits. Red blood cells and hemoglobin, immune cells, proinflammatory cytokines, and peroxidases are directly or indirectly involved in the regulation of neuroinflammation and oxidative stress in the central nervous system after SAH. This review explores the role of various cellular and acellular components in secondary inflammation and oxidative stress after SAH, and aims to provide new ideas for clinical treatment to improve the prognosis of SAH.

Physical Exercise Protects Against Endothelial Dysfunction in Cardiovascular and Metabolic Diseases

Increasing evidence shows that endothelial cells play critical roles in maintaining vascular homeostasis, regulating vascular tone, inhibiting inflammatory response, suppressing lipid leakage, and preventing thrombosis. The damage or injury of endothelial cells induced by physical, chemical, and biological risk factors is a leading contributor to the development of mortal cardiovascular and cerebrovascular diseases. However, the underlying mechanism of endothelial injury remains to be elucidated. Notably, no drugs effectively targeting and mending injured vascular endothelial cells have been approved for clinical practice. There is an urgent need to understand pathways important for repairing injured vasculature that can be targeted with novel therapies. Exercise training-induced protection to endothelial injury has been well documented in clinical trials, and the underlying mechanism has been explored in animal models. This review mainly summarizes the protective effects of exercise on vascular endothelium and the recently identified potential therapeutic targets for endothelial dysfunction.

Breast cancer type 1 and neurodegeneration: consequences of deficient DNA repair

Numerous cellular processes, including toxic protein aggregation and oxidative stress, have been studied extensively as potential mechanisms underlying neurodegeneration. However, limited therapeutic efficacy targeting these processes has prompted other mechanisms to be explored. Previous research has emphasized a link between cellular senescence and neurodegeneration, where senescence induced by excess DNA damage and deficient DNA repair results in structural and functional changes that ultimately contribute to brain dysfunction and increased vulnerability for neurodegeneration. Specific DNA repair proteins, such as breast cancer type 1, have been associated with both stress-induced senescence and neurodegenerative diseases, however, specific mechanisms remain unclear. Therefore, this review explores DNA damage-induced senescence in the brain as a driver of neurodegeneration, with particular focus on breast cancer type 1, and its potential contribution to sex-specific differences associated with neurodegenerative disease.

The Roles of Nitric Oxide Synthase/Nitric Oxide Pathway in the Pathology of Vascular Dementia and Related Therapeutic Approaches

Vascular dementia (VaD) is the second most common form of dementia worldwide. It is caused by cerebrovascular disease, and patients often show severe impairments of advanced cognitive abilities. Nitric oxide synthase (NOS) and nitric oxide (NO) play vital roles in the pathogenesis of VaD. The functions of NO are determined by its concentration and bioavailability, which are regulated by NOS activity. The activities of different NOS subtypes in the brain are partitioned. Pathologically, endothelial NOS is inactivated, which causes insufficient NO production and aggravates oxidative stress before inducing cerebrovascular endothelial dysfunction, while neuronal NOS is overactive and can produce excessive NO to cause neurotoxicity. Meanwhile, inflammation stimulates the massive expression of inducible NOS, which also produces excessive NO and then induces neuroinflammation. The vicious circle of these kinds of damage having impacts on each other finally leads to VaD. This review summarizes the roles of the NOS/NO pathway in the pathology of VaD and also proposes some potential therapeutic methods that target this pathway in the hope of inspiring novel ideas for VaD therapeutic approaches.

Vascular Senescence: A Potential Bridge Between Physiological Aging and Neurogenic Decline

The adult mammalian brain contains distinct neurogenic niches harboring populations of neural stem cells (NSCs) with the capacity to sustain the generation of specific subtypes of neurons during the lifetime. However, their ability to produce new progeny declines with age. The microenvironment of these specialized niches provides multiple cellular and molecular signals that condition NSC behavior and potential. Among the different niche components, vasculature has gained increasing interest over the years due to its undeniable role in NSC regulation and its therapeutic potential for neurogenesis enhancement. NSCs are uniquely positioned to receive both locally secreted factors and adhesion-mediated signals derived from vascular elements. Furthermore, studies of parabiosis indicate that NSCs are also exposed to blood-borne factors, sensing and responding to the systemic circulation. Both structural and functional alterations occur in vasculature with age at the cellular level that can affect the proper extrinsic regulation of NSCs. Additionally, blood exchange experiments in heterochronic parabionts have revealed that age-associated changes in blood composition also contribute to adult neurogenesis impairment in the elderly. Although the mechanisms of vascular- or blood-derived signaling in aging are still not fully understood, a general feature of organismal aging is the accumulation of senescent cells, which act as sources of inflammatory and other detrimental signals that can negatively impact on neighboring cells. This review focuses on the interactions between vascular senescence, circulating pro-senescence factors and the decrease in NSC potential during aging. Understanding the mechanisms of NSC dynamics in the aging brain could lead to new therapeutic approaches, potentially include senolysis, to target age-dependent brain decline.